Problem p02376 (C++) — buggy submission, verdict: Runtime Error

#include <algorithm>
#include <fstream>
#include <iomanip>
#include <iostream>
#include <limits>
#include <list>
#include <queue>
#include <string>
#include <vector>

// УБРАТЬ!
using namespace std;

// Net class:
template <class Edge> class Net {
private:
  typedef Edge *EdgePointer;
  typedef pair<EdgePointer, EdgePointer> Arc;
  list<Arc> edges;
  vector<list<Arc>> innerEdges;
  vector<list<Arc>> outerEdges;

  class UniversalEdgeIterator {
    friend class Net;

  private:
    list<Arc> *edgesList;
    typename list<Arc>::iterator edgeIterator;

    bool validated;
    enum UniversalIteratorType { inner, outer, all };
    UniversalIteratorType iteratorType;

    UniversalEdgeIterator(list<Arc> *edgesList,
                          const UniversalIteratorType &getIteratorType) {
      this->edgesList = edgesList;
      this->iteratorType = iteratorType;
      validated = false;
    }

    void validate() {
      if (validated)
        return;

      else {
        validated = true;
        begin();
      }
    }

  public:
    typedef UniversalIteratorType IteratorType;

    UniversalEdgeIterator() {
      edgesList = nullptr;
      validated = false;
    }

    // Iterator methods:
    void begin() { edgeIterator = edgesList->begin(); }

    void move() { edgeIterator = next(edgeIterator); }

    bool end() const {
      return edgesList->size() == 0 || edgeIterator == edgesList->end();
    }

    // Getters:
    Edge getEdge() const {
      // cout << "s" << edgesList->size() << endl;
      return *(*edgeIterator).first;
    }

    Edge getReversedEdge() const { return *(*edgeIterator).second; }

    // Setter:
    void increaseFlow(const typename Edge::FlowType &delta) const {
      (*edgeIterator).first->flow += delta;
      (*edgeIterator).second->flow -= delta;
    }

    // Other:
    IteratorType getIteratorType() const { return iteratorType; }
  };

  UniversalEdgeIterator allEdgesIterator;
  vector<UniversalEdgeIterator> innerEdgesIterators;
  vector<UniversalEdgeIterator> outerEdgesIterators;

public:
  typedef UniversalEdgeIterator EdgeIterator;
  typedef typename Edge::IndexType IndexType;
  IndexType source;
  IndexType sink;

  // Constructors, destructors:
  Net(const IndexType &verticesCount) {
    allEdgesIterator = EdgeIterator(&edges, EdgeIterator::IteratorType::all);
    innerEdges.resize(verticesCount);
    outerEdges.resize(verticesCount);
    innerEdgesIterators.resize(verticesCount);
    outerEdgesIterators.resize(verticesCount);

    for (unsigned i = 0; i < verticesCount; i++) {
      innerEdgesIterators[i] =
          EdgeIterator(&innerEdges[i], EdgeIterator::IteratorType::inner);
      outerEdgesIterators[i] =
          EdgeIterator(&outerEdges[i], EdgeIterator::IteratorType::outer);
    }
  }

  ~Net() {
    for (const Arc &arc : edges)
      delete arc.first;
  }

  // Setters:
  void addEdge(const Edge &edge) {
    EdgePointer edgePointer = new Edge(edge);
    EdgePointer reversedEdgePointer = new Edge(edge.reversed());

    edges.push_back(make_pair(edgePointer, reversedEdgePointer));
    outerEdges[edgePointer->from].push_back(
        make_pair(edgePointer, reversedEdgePointer));
    innerEdges[edgePointer->to].push_back(
        make_pair(edgePointer, reversedEdgePointer));

    edges.push_back(make_pair(reversedEdgePointer, edgePointer));
    outerEdges[reversedEdgePointer->from].push_back(
        make_pair(reversedEdgePointer, edgePointer));
    innerEdges[reversedEdgePointer->to].push_back(
        make_pair(reversedEdgePointer, edgePointer));

    allEdgesIterator.validate();
    outerEdgesIterators[edgePointer->from].validate();
    outerEdgesIterators[edgePointer->to].validate();
    innerEdgesIterators[edgePointer->from].validate();
    innerEdgesIterators[edgePointer->to].validate();
  }

  // Getters:
  EdgeIterator &getAllEdgesIterator() { return allEdgesIterator; }

  EdgeIterator getConstAllEdgesIterator() const { return allEdgesIterator; }

  EdgeIterator &getInnerEdgeIterator(const IndexType &vertex) {
    return innerEdgesIterators[vertex];
  }

  EdgeIterator getConstInnerEdgeIterator(const IndexType &vertex) const {
    return innerEdgesIterators[vertex];
  }

  EdgeIterator &getOuterEdgeIterator(const IndexType &vertex) {
    return outerEdgesIterators[vertex];
  }

  EdgeIterator getConstOuterEdgeIterator(const IndexType &vertex) const {
    return outerEdgesIterators[vertex];
  }

  // Info:
  IndexType getVerticesCount() const { return innerEdges.size(); }

  IndexType getEdgesCount() const { return edges.size(); }
};

// Flow addons:
template <class Edge>
const typename Edge::FlowType
getFlowFromOrToVertex(typename Net<Edge>::EdgeIterator iter) {
  typename Edge::FlowType flow = 0;

  for (iter.begin(); !iter.end(); iter.move())
    flow += iter.getEdge().flow;

  return flow;
}

template <class Edge> bool isFlowValid(const Net<Edge> &net) {
  typename Net<Edge>::EdgeIterator iter = net.getConstAllEdgesIterator();

  for (iter.begin(); !iter.end(); iter.move())
    if (iter.getEdge().flow > iter.getEdge().capacity ||
        iter.getEdge().flow != -iter.getReversedEdge().flow)
      return false;

  for (typename Edge::IndexType vertex = 0; vertex < net.getVerticesCount();
       vertex++) {
    if (vertex == net.source || vertex == net.sink)
      break;

    typename Edge::FlowType innerFlow =
        getFlowFromOrToVertex<Edge>(net.getConstInnerEdgeIterator(vertex));
    typename Edge::FlowType outerFlow =
        getFlowFromOrToVertex<Edge>(net.getConstOuterEdgeIterator(vertex));

    if (innerFlow != outerFlow)
      return false;
  }

  return true;
}

template <class Edge>
typename Edge::FlowType getFlowWithoutCheck(const Net<Edge> &net) {
  return getFlowFromOrToVertex<Edge>(net.getConstOuterEdgeIterator(net.source));
}

template <class Edge>
typename Edge::FlowType getFlowWithCheck(const Net<Edge> &net) {
  if (isFlowValid(net))
    return getFlowWithoutCheck(net);

  else
    throw("Net exeption: invalid flow!");
}

// Global discharge algorithm:
template <class Edge>
void push(Net<Edge> &net, const typename Net<Edge>::EdgeIterator &iter,
          const typename Edge::FlowType &pushingFlow,
          vector<typename Edge::FlowType> &excess) {
  iter.increaseFlow(pushingFlow);
  Edge edge = iter.getEdge();

  if (edge.from != net.source && edge.from != net.sink)
    excess[edge.from] -= pushingFlow;

  if (edge.to != net.source && edge.to != net.sink)
    excess[edge.to] += pushingFlow;
}

template <class Edge>
void relabel(const Net<Edge> &net, const typename Edge::IndexType &vertex,
             vector<typename Edge::IndexType> &height) {
  typename Edge::IndexType minHeight =
      numeric_limits<typename Edge::IndexType>::max();

  typename Net<Edge>::EdgeIterator iter = net.getConstOuterEdgeIterator(vertex);

  for (iter.begin(); !iter.end(); iter.move()) {
    Edge edge = iter.getEdge();

    if (edge.residualCapacity() > 0)
      minHeight = min<typename Edge::IndexType>(minHeight, height[edge.to]);
  }

  height[vertex] = minHeight + 1;
}

template <class Edge>
inline void discharge(Net<Edge> &net, const typename Edge::IndexType &vertex,
                      vector<typename Edge::FlowType> &excess,
                      vector<typename Edge::IndexType> &height) {
  while (excess[vertex] > 0) {
    typename Net<Edge>::EdgeIterator &iter = net.getOuterEdgeIterator(vertex);

    if (iter.end()) {
      relabel(net, vertex, height);
      iter.begin();
    }

    else {
      Edge edge = iter.getEdge();

      if (edge.residualCapacity() > 0 &&
          height[vertex] == height[edge.to] + 1) {
        typename Edge::FlowType pushingFlow = min<typename Edge::FlowType>(
            excess[edge.from], edge.residualCapacity());
        push(net, iter, pushingFlow, excess);
      }

      else
        iter.move();
    }
  }
}

template <class Edge> void setMaxFlowWithPreflowPush(Net<Edge> &net) {
  vector<typename Edge::FlowType> excess(net.getVerticesCount(), 0);
  vector<typename Edge::IndexType> height(net.getVerticesCount(), 0);
  height[net.source] = net.getVerticesCount();

  typename Net<Edge>::EdgeIterator iter =
      net.getConstOuterEdgeIterator(net.source);

  for (iter.begin(); !iter.end(); iter.move())
    push(net, iter, iter.getEdge().residualCapacity(), excess);

  while (true) {
    bool discharged = false;

    for (typename Edge::IndexType vertex = 0; vertex < net.getVerticesCount();
         vertex++) {
      if (excess[vertex] && vertex != net.source && vertex != net.sink) {
        discharge(net, vertex, excess, height);
        discharged = true;
      }
    }

    if (!discharged)
      break;
  }
}

// Dinic Blocking flow algorithm:
template <class Edge>
typename Edge::FlowType
tryPushFlow(Net<Edge> &layeredNet, const typename Edge::IndexType &vertex,
            const typename Edge::FlowType &pushingFlow =
                numeric_limits<typename Edge::FlowType>::max()) {
  if (vertex == layeredNet.sink || pushingFlow == 0)
    return pushingFlow;

  for (typename Net<Edge>::EdgeIterator iter =
           layeredNet.getConstOuterEdgeIterator(vertex);
       !iter.end(); iter.move()) {
    Edge edge = iter.getEdge();

    if (edge.capacity == 0)
      continue;

    typename Edge::FlowType newPushingFlow =
        min<typename Edge::FlowType>(pushingFlow, edge.residualCapacity());
    typename Edge::FlowType pushedFlow =
        tryPushFlow(layeredNet, edge.to, newPushingFlow);

    if (pushedFlow != 0) {
      iter.increaseFlow(pushedFlow);
      return pushedFlow;
    }
  }

  if (!layeredNet.getOuterEdgeIterator(vertex).end())
    layeredNet.getOuterEdgeIterator(vertex).move();

  return 0;
}

template <class Edge> void setBlockingFlowWithDinic(Net<Edge> &layeredNet) {
  while (tryPushFlow(layeredNet, layeredNet.source) != 0) {
  };
}

// Malhotra-Kumar-Maheshwari Blocking flow algorithm:
template <class Edge>
inline typename Edge::FlowType
setPotentialOneSide(typename Net<Edge>::EdgeIterator iter) {
  typename Edge::FlowType potential = 0;

  for (iter.begin(); !iter.end(); iter.move())
    potential += iter.getEdge().residualCapacity();

  return potential;
}

template <class Edge>
inline typename Edge::FlowType
getPotential(const Net<Edge> &net, const typename Edge::IndexType &vertex,
             const vector<typename Edge::FlowType> &innerPotential,
             const vector<typename Edge::FlowType> &outerPotential) {
  if (vertex == net.source)
    return outerPotential[vertex];

  else if (vertex == net.sink)
    return innerPotential[vertex];

  else
    return min<typename Edge::FlowType>(outerPotential[vertex],
                                        innerPotential[vertex]);
}

template <class Edge>
inline void deleteVertexOneSide(const Net<Edge> &layeredNet,
                                typename Net<Edge>::EdgeIterator iter,
                                vector<typename Edge::FlowType> &innerPotential,
                                vector<typename Edge::FlowType> &outerPotential,
                                vector<bool> &isDeleted) {
  for (iter.begin(); !iter.end(); iter.move()) {
    Edge edge = iter.getEdge();

    if (edge.capacity == 0)
      continue;

    typename Edge::IndexType nextVertex =
        (iter.getIteratorType() == Net<Edge>::EdgeIterator::IteratorType::outer
             ? edge.to
             : edge.from);
    (iter.getIteratorType() == Net<Edge>::EdgeIterator::IteratorType::outer
         ? innerPotential[nextVertex]
         : outerPotential[nextVertex]) -= edge.residualCapacity();

    if (getPotential(layeredNet, nextVertex, innerPotential, outerPotential) ==
        0)
      deleteVertex(layeredNet, nextVertex, innerPotential, outerPotential,
                   isDeleted);
  }
}

template <class Edge>
void deleteVertex(const Net<Edge> &layeredNet,
                  const typename Edge::IndexType &vertex,
                  vector<typename Edge::FlowType> &innerPotential,
                  vector<typename Edge::FlowType> &outerPotential,
                  vector<bool> &isDeleted) {
  if (isDeleted[vertex])
    return;

  isDeleted[vertex] = true;
  deleteVertexOneSide<Edge>(layeredNet,
                            layeredNet.getConstOuterEdgeIterator(vertex),
                            innerPotential, outerPotential, isDeleted);
  deleteVertexOneSide<Edge>(layeredNet,
                            layeredNet.getConstInnerEdgeIterator(vertex),
                            innerPotential, outerPotential, isDeleted);
}

template <typename Edge>
void pushFlowFromRoot(Net<Edge> &layeredNet,
                      const typename Edge::IndexType &root,
                      const typename Edge::FlowType &pushingFlow,
                      const typename Edge::IndexType &destination,
                      vector<typename Edge::FlowType> &innerPotential,
                      vector<typename Edge::FlowType> &outerPotential,
                      const vector<bool> &isDeleted) {
  // BFS init:
  queue<typename Edge::IndexType> verticesQueue;
  vector<bool> used(layeredNet.getVerticesCount(), false);
  verticesQueue.push(root);
  used[root] = true;

  // Other data init:
  vector<typename Edge::FlowType> excessOrLack(layeredNet.getVerticesCount(),
                                               0);
  excessOrLack[root] = pushingFlow;

  // BFS:
  while (!verticesQueue.empty()) {
    typename Edge::IndexType vertex = verticesQueue.front();
    verticesQueue.pop();

    if (vertex == destination)
      break;

    for (typename Net<Edge>::EdgeIterator &iter =
             (destination == layeredNet.sink
                  ? layeredNet.getOuterEdgeIterator(vertex)
                  : layeredNet.getInnerEdgeIterator(vertex));
         !iter.end(); iter.move()) {
      Edge edge = iter.getEdge();
      typename Edge::IndexType nextVertex =
          (destination == layeredNet.sink ? edge.to : edge.from);

      if (edge.capacity > 0 && !isDeleted[nextVertex]) {
        if (!used[nextVertex]) {
          verticesQueue.push(nextVertex);
          used[nextVertex] = true;
        }

        typename Edge::FlowType pushedFlow = min<typename Edge::FlowType>(
            excessOrLack[vertex], edge.residualCapacity());
        excessOrLack[vertex] -= pushedFlow;
        excessOrLack[nextVertex] += pushedFlow;
        iter.increaseFlow(pushedFlow);
        outerPotential[edge.from] -= pushedFlow;
        innerPotential[edge.to] -= pushedFlow;
      }

      if (excessOrLack[vertex] == 0)
        break;
    }
  }
}

template <class Edge>
void setBlockingFlowWithMalhotraKumarMaheshwari(Net<Edge> &layeredNet) {
  // Initialize potentials:
  vector<typename Edge::FlowType> innerPotential(layeredNet.getVerticesCount());
  vector<typename Edge::FlowType> outerPotential(layeredNet.getVerticesCount());

  for (typename Edge::IndexType vertex = 0;
       vertex < layeredNet.getVerticesCount(); vertex++) {
    innerPotential[vertex] =
        setPotentialOneSide<Edge>(layeredNet.getConstInnerEdgeIterator(vertex));
    outerPotential[vertex] =
        setPotentialOneSide<Edge>(layeredNet.getConstOuterEdgeIterator(vertex));
  }

  // Initialize deleted vertices:
  vector<bool> isDeleted(layeredNet.getVerticesCount(), false);

  // Main cycle:
  while (true) {
    // Deleting traverse:
    for (typename Edge::IndexType vertex = 0;
         vertex < layeredNet.getVerticesCount(); vertex++)
      if (!isDeleted[vertex] &&
          getPotential(layeredNet, vertex, innerPotential, outerPotential) == 0)
        deleteVertex(layeredNet, vertex, innerPotential, outerPotential,
                     isDeleted);

    if (isDeleted[layeredNet.source] || isDeleted[layeredNet.sink])
      break;

    // Finding root:
    typename Edge::IndexType root = layeredNet.source;

    for (typename Edge::IndexType vertex = 0;
         vertex < layeredNet.getVerticesCount(); vertex++)
      if (!isDeleted[vertex] &&
          getPotential(layeredNet, vertex, innerPotential, outerPotential) <=
              getPotential(layeredNet, root, innerPotential, outerPotential))
        root = vertex;

    typename Edge::FlowType rootPotential =
        getPotential(layeredNet, root, innerPotential, outerPotential);

    // Pushing flow through the root:
    pushFlowFromRoot(layeredNet, root, rootPotential, layeredNet.sink,
                     innerPotential, outerPotential, isDeleted);
    pushFlowFromRoot(layeredNet, root, rootPotential, layeredNet.source,
                     innerPotential, outerPotential, isDeleted);
  }
}

// Global Max Flow augmenting paths algorithm:
template <class Edge> Net<Edge> buildLayeredNetwork(const Net<Edge> &net) {
  // BFS init:
  queue<typename Edge::IndexType> verticesQueue;
  vector<bool> used(net.getVerticesCount(), false);
  verticesQueue.push(net.source);

  // Layered Net init:
  Net<Edge> layeredNet(net.getVerticesCount());
  layeredNet.source = net.source;
  layeredNet.sink = net.sink;
  vector<typename Edge::IndexType> layers(
      net.getVerticesCount(), numeric_limits<typename Edge::IndexType>::max());
  layers[net.source] = 0;

  // BFS:
  while (!verticesQueue.empty()) {
    typename Edge::IndexType vertex = verticesQueue.front();
    verticesQueue.pop();

    if (used[vertex])
      continue;

    used[vertex] = true;

    typename Net<Edge>::EdgeIterator iter =
        net.getConstOuterEdgeIterator(vertex);

    for (iter.begin(); !iter.end(); iter.move()) {
      Edge edge = iter.getEdge();

      if (edge.residualCapacity() > 0 &&
          layers[edge.from] + 1 <= layers[edge.to]) {
        verticesQueue.push(edge.to);

        Edge residualEdge = edge;
        residualEdge.capacity = edge.residualCapacity();
        residualEdge.flow = 0;
        layeredNet.addEdge(residualEdge);
        layers[edge.to] = layers[edge.from] + 1;
      }
    }
  }

  return layeredNet;
}

// Класс bfs iterator, который будет делать все логику:
template <class Edge>
void transferFlowFromLayeredNetworkToNetwork(Net<Edge> &layeredNet,
                                             Net<Edge> &net) {
  // BFS init:
  queue<typename Edge::IndexType> verticesQueue;
  vector<bool> used(net.getVerticesCount(), false);
  verticesQueue.push(net.source);

  // Layered Net init:
  vector<typename Edge::IndexType> layers(
      net.getVerticesCount(), numeric_limits<typename Edge::IndexType>::max());
  layers[net.source] = 0;

  // BFS:
  while (!verticesQueue.empty()) {
    typename Edge::IndexType vertex = verticesQueue.front();
    verticesQueue.pop();

    if (used[vertex])
      continue;

    used[vertex] = true;

    typename Net<Edge>::EdgeIterator iter =
        net.getConstOuterEdgeIterator(vertex);
    typename Net<Edge>::EdgeIterator &layeredNetIter =
        layeredNet.getOuterEdgeIterator(vertex);
    layeredNetIter.begin();

    for (iter.begin(); !iter.end() && !layeredNetIter.end(); iter.move()) {
      Edge edge = iter.getEdge();

      if (edge.residualCapacity() > 0 &&
          layers[edge.from] + 1 <= layers[edge.to]) {
        verticesQueue.push(edge.to);

        layers[edge.to] = layers[edge.from] + 1;

        while (layeredNetIter.getEdge().capacity == 0)
          layeredNetIter.move();

        iter.increaseFlow(layeredNetIter.getEdge().flow);
        layeredNetIter.move();
      }
    }
  }
}

// Сделать классом с кастомным виртуальным blocking flow:
template <class Edge> void setMaxFlowWithAugmentingPaths(Net<Edge> &net) {
  while (true) {
    Net<Edge> layeredNet = buildLayeredNetwork(net);
    setBlockingFlowWithMalhotraKumarMaheshwari(layeredNet);

    if (getFlowWithCheck(layeredNet) == 0)
      break;

    else {
      transferFlowFromLayeredNetworkToNetwork(layeredNet, net);
    }
  }
}

// --------------------------------------------------

// My custom Edge:
template <typename FirstType = unsigned, typename SecondType = long long>
struct Edge {
  typedef FirstType IndexType;
  typedef SecondType FlowType;
  IndexType from;
  IndexType to;
  FlowType flow;
  FlowType capacity;

  Edge(const IndexType &from, const IndexType &to, const FlowType &capacity) {
    this->from = from;
    this->to = to;
    this->flow = 0;
    this->capacity = capacity;
  }

  FlowType residualCapacity() const { return capacity - flow; }

  Edge reversed() const { return Edge(to, from, 0); }
};

// Custom inputs/outputs:
template <class Edge> void printEdge(const Edge &edge, ostream &os = cout) {
  os << edge.from << " -> " << edge.to << " (" << edge.flow << "/"
     << edge.capacity << ")";
}

template <class Edge> void printNet(Net<Edge> &net, ostream &os = cout) {
  for (typename Edge::IndexType vertex = 0; vertex < net.getVerticesCount();
       vertex++) {
    typename Net<Edge>::EdgeIterator iter =
        net.getConstOuterEdgeIterator(vertex);

    for (iter.begin(); !iter.end(); iter.move()) {
      printEdge(iter.getEdge(), os);
      os << " ";
    }

    os << endl;
  }
}

/*
// Сделать нормальный input.
long long solve () {
        unsigned verticesCount;
        cin >> verticesCount;
        const long long maxCapacity = verticesCount * 1000 + 1;
        long long positiveSum = 0;

        Net<Edge<unsigned, long long> > net(verticesCount + 2);
        net.source = verticesCount;
        net.sink = verticesCount + 1;

        for (unsigned i = 0; i < verticesCount; i ++) {
                long long usability;
                cin >> usability;

                if (usability > 0) {
                        positiveSum += usability;
                        net.addEdge(Edge<unsigned, long long>(net.source, i,
usability));
                }

                else
                        net.addEdge(Edge<unsigned, long long>(i, net.sink, -
usability));
        }

        for (unsigned from = 0; from < verticesCount; from ++) {
                unsigned nextEdgesCount;
                cin >> nextEdgesCount;

                for (unsigned edge = 0; edge < nextEdgesCount; edge ++) {
                        unsigned to;
                        cin >> to;
                        net.addEdge(Edge<unsigned, long long>(from, to - 1,
maxCapacity));
                }
        }

        setMaxFlowWithPreflowPush(net);
        return positiveSum - getFlowWithCheck(net);
}
*/

int main() {
  unsigned verticesCount, edgesCount;
  cin >> verticesCount >> edgesCount;

  Net<Edge<unsigned, long long>> net(verticesCount);
  net.source = 0;
  net.sink = verticesCount - 1;

  for (unsigned i = 0; i < edgesCount; i++) {
    unsigned from, to;
    long long capacity;
    cin >> from >> to >> capacity;
    net.addEdge(Edge<unsigned, long long>(from, to, capacity));
  }

  setMaxFlowWithPreflowPush(net);
  cout << getFlowWithCheck(net) << endl;

  return 0;
}


Error: -11

Fixed submission:

#include <algorithm>
#include <fstream>
#include <iomanip>
#include <iostream>
#include <limits>
#include <list>
#include <queue>
#include <string>
#include <vector>

// УБРАТЬ!
using namespace std;

// Net class:
template <class Edge> class Net {
private:
  typedef Edge *EdgePointer;
  typedef pair<EdgePointer, EdgePointer> Arc;
  list<Arc> edges;
  vector<list<Arc>> innerEdges;
  vector<list<Arc>> outerEdges;

  class UniversalEdgeIterator {
    friend class Net;

  private:
    list<Arc> *edgesList;
    typename list<Arc>::iterator edgeIterator;

    bool validated;
    enum UniversalIteratorType { inner, outer, all };
    UniversalIteratorType iteratorType;

    UniversalEdgeIterator(list<Arc> *edgesList,
                          const UniversalIteratorType &getIteratorType) {
      this->edgesList = edgesList;
      this->iteratorType = iteratorType;
      validated = false;
    }

    void validate() {
      if (validated)
        return;

      else {
        validated = true;
        begin();
      }
    }

  public:
    typedef UniversalIteratorType IteratorType;

    UniversalEdgeIterator() {
      edgesList = nullptr;
      validated = false;
    }

    // Iterator methods:
    void begin() { edgeIterator = edgesList->begin(); }

    void move() { edgeIterator = next(edgeIterator); }

    bool end() const {
      return edgesList->size() == 0 || edgeIterator == edgesList->end();
    }

    // Getters:
    Edge getEdge() const {
      // cout << "s" << edgesList->size() << endl;
      return *(*edgeIterator).first;
    }

    Edge getReversedEdge() const { return *(*edgeIterator).second; }

    // Setter:
    void increaseFlow(const typename Edge::FlowType &delta) const {
      (*edgeIterator).first->flow += delta;
      (*edgeIterator).second->flow -= delta;
    }

    // Other:
    IteratorType getIteratorType() const { return iteratorType; }
  };

  UniversalEdgeIterator allEdgesIterator;
  vector<UniversalEdgeIterator> innerEdgesIterators;
  vector<UniversalEdgeIterator> outerEdgesIterators;

public:
  typedef UniversalEdgeIterator EdgeIterator;
  typedef typename Edge::IndexType IndexType;
  IndexType source;
  IndexType sink;

  // Constructors, destructors:
  Net(const IndexType &verticesCount) {
    allEdgesIterator = EdgeIterator(&edges, EdgeIterator::IteratorType::all);
    innerEdges.resize(verticesCount);
    outerEdges.resize(verticesCount);
    innerEdgesIterators.resize(verticesCount);
    outerEdgesIterators.resize(verticesCount);

    for (unsigned i = 0; i < verticesCount; i++) {
      innerEdgesIterators[i] =
          EdgeIterator(&innerEdges[i], EdgeIterator::IteratorType::inner);
      outerEdgesIterators[i] =
          EdgeIterator(&outerEdges[i], EdgeIterator::IteratorType::outer);
    }
  }

  ~Net() {
    for (const Arc &arc : edges)
      delete arc.first;
  }

  // Setters:
  void addEdge(const Edge &edge) {
    EdgePointer edgePointer = new Edge(edge);
    EdgePointer reversedEdgePointer = new Edge(edge.reversed());

    edges.push_back(make_pair(edgePointer, reversedEdgePointer));
    outerEdges[edgePointer->from].push_back(
        make_pair(edgePointer, reversedEdgePointer));
    innerEdges[edgePointer->to].push_back(
        make_pair(edgePointer, reversedEdgePointer));

    edges.push_back(make_pair(reversedEdgePointer, edgePointer));
    outerEdges[reversedEdgePointer->from].push_back(
        make_pair(reversedEdgePointer, edgePointer));
    innerEdges[reversedEdgePointer->to].push_back(
        make_pair(reversedEdgePointer, edgePointer));

    allEdgesIterator.validate();
    outerEdgesIterators[edgePointer->from].validate();
    outerEdgesIterators[edgePointer->to].validate();
    innerEdgesIterators[edgePointer->from].validate();
    innerEdgesIterators[edgePointer->to].validate();
  }

  // Getters:
  EdgeIterator &getAllEdgesIterator() { return allEdgesIterator; }

  EdgeIterator getConstAllEdgesIterator() const { return allEdgesIterator; }

  EdgeIterator &getInnerEdgeIterator(const IndexType &vertex) {
    return innerEdgesIterators[vertex];
  }

  EdgeIterator getConstInnerEdgeIterator(const IndexType &vertex) const {
    return innerEdgesIterators[vertex];
  }

  EdgeIterator &getOuterEdgeIterator(const IndexType &vertex) {
    return outerEdgesIterators[vertex];
  }

  EdgeIterator getConstOuterEdgeIterator(const IndexType &vertex) const {
    return outerEdgesIterators[vertex];
  }

  // Info:
  IndexType getVerticesCount() const { return innerEdges.size(); }

  IndexType getEdgesCount() const { return edges.size(); }
};

// Flow addons:
template <class Edge>
const typename Edge::FlowType
getFlowFromOrToVertex(typename Net<Edge>::EdgeIterator iter) {
  typename Edge::FlowType flow = 0;

  for (iter.begin(); !iter.end(); iter.move())
    flow += iter.getEdge().flow;

  return flow;
}

template <class Edge> bool isFlowValid(const Net<Edge> &net) {
  typename Net<Edge>::EdgeIterator iter = net.getConstAllEdgesIterator();

  for (iter.begin(); !iter.end(); iter.move())
    if (iter.getEdge().flow > iter.getEdge().capacity ||
        iter.getEdge().flow != -iter.getReversedEdge().flow)
      return false;

  for (typename Edge::IndexType vertex = 0; vertex < net.getVerticesCount();
       vertex++) {
    if (vertex == net.source || vertex == net.sink)
      break;

    typename Edge::FlowType innerFlow =
        getFlowFromOrToVertex<Edge>(net.getConstInnerEdgeIterator(vertex));
    typename Edge::FlowType outerFlow =
        getFlowFromOrToVertex<Edge>(net.getConstOuterEdgeIterator(vertex));

    if (innerFlow != outerFlow)
      return false;
  }

  return true;
}

template <class Edge>
typename Edge::FlowType getFlowWithoutCheck(const Net<Edge> &net) {
  return getFlowFromOrToVertex<Edge>(net.getConstOuterEdgeIterator(net.source));
}

template <class Edge>
typename Edge::FlowType getFlowWithCheck(const Net<Edge> &net) {
  if (isFlowValid(net))
    return getFlowWithoutCheck(net);

  else
    throw("Net exeption: invalid flow!");
}

// Global discharge algorithm:
template <class Edge>
void push(Net<Edge> &net, const typename Net<Edge>::EdgeIterator &iter,
          const typename Edge::FlowType &pushingFlow,
          vector<typename Edge::FlowType> &excess) {
  iter.increaseFlow(pushingFlow);
  Edge edge = iter.getEdge();

  if (edge.from != net.source && edge.from != net.sink)
    excess[edge.from] -= pushingFlow;

  if (edge.to != net.source && edge.to != net.sink)
    excess[edge.to] += pushingFlow;
}

template <class Edge>
void relabel(const Net<Edge> &net, const typename Edge::IndexType &vertex,
             vector<typename Edge::IndexType> &height) {
  typename Edge::IndexType minHeight =
      numeric_limits<typename Edge::IndexType>::max();

  typename Net<Edge>::EdgeIterator iter = net.getConstOuterEdgeIterator(vertex);

  for (iter.begin(); !iter.end(); iter.move()) {
    Edge edge = iter.getEdge();

    if (edge.residualCapacity() > 0)
      minHeight = min<typename Edge::IndexType>(minHeight, height[edge.to]);
  }

  height[vertex] = minHeight + 1;
}

template <class Edge>
inline void discharge(Net<Edge> &net, const typename Edge::IndexType &vertex,
                      vector<typename Edge::FlowType> &excess,
                      vector<typename Edge::IndexType> &height) {
  while (excess[vertex] > 0) {
    typename Net<Edge>::EdgeIterator &iter = net.getOuterEdgeIterator(vertex);

    if (iter.end()) {
      relabel(net, vertex, height);
      iter.begin();
    }

    else {
      Edge edge = iter.getEdge();

      if (edge.residualCapacity() > 0 &&
          height[vertex] == height[edge.to] + 1) {
        typename Edge::FlowType pushingFlow = min<typename Edge::FlowType>(
            excess[edge.from], edge.residualCapacity());
        push(net, iter, pushingFlow, excess);
      }

      else
        iter.move();
    }
  }
}

template <class Edge> void setMaxFlowWithPreflowPush(Net<Edge> &net) {
  vector<typename Edge::FlowType> excess(net.getVerticesCount(), 0);
  vector<typename Edge::IndexType> height(net.getVerticesCount(), 0);
  height[net.source] = net.getVerticesCount();

  typename Net<Edge>::EdgeIterator iter =
      net.getConstOuterEdgeIterator(net.source);

  for (iter.begin(); !iter.end(); iter.move())
    push(net, iter, iter.getEdge().residualCapacity(), excess);

  while (true) {
    bool discharged = false;

    for (typename Edge::IndexType vertex = 0; vertex < net.getVerticesCount();
         vertex++) {
      if (excess[vertex] && vertex != net.source && vertex != net.sink) {
        discharge(net, vertex, excess, height);
        discharged = true;
      }
    }

    if (!discharged)
      break;
  }
}

// Dinic Blocking flow algorithm:
template <class Edge>
typename Edge::FlowType
tryPushFlow(Net<Edge> &layeredNet, const typename Edge::IndexType &vertex,
            const typename Edge::FlowType &pushingFlow =
                numeric_limits<typename Edge::FlowType>::max()) {
  if (vertex == layeredNet.sink || pushingFlow == 0)
    return pushingFlow;

  for (typename Net<Edge>::EdgeIterator iter =
           layeredNet.getConstOuterEdgeIterator(vertex);
       !iter.end(); iter.move()) {
    Edge edge = iter.getEdge();

    if (edge.capacity == 0)
      continue;

    typename Edge::FlowType newPushingFlow =
        min<typename Edge::FlowType>(pushingFlow, edge.residualCapacity());
    typename Edge::FlowType pushedFlow =
        tryPushFlow(layeredNet, edge.to, newPushingFlow);

    if (pushedFlow != 0) {
      iter.increaseFlow(pushedFlow);
      return pushedFlow;
    }
  }

  if (!layeredNet.getOuterEdgeIterator(vertex).end())
    layeredNet.getOuterEdgeIterator(vertex).move();

  return 0;
}

template <class Edge> void setBlockingFlowWithDinic(Net<Edge> &layeredNet) {
  while (tryPushFlow(layeredNet, layeredNet.source) != 0) {
  };
}

// Malhotra-Kumar-Maheshwari Blocking flow algorithm:
template <class Edge>
inline typename Edge::FlowType
setPotentialOneSide(typename Net<Edge>::EdgeIterator iter) {
  typename Edge::FlowType potential = 0;

  for (iter.begin(); !iter.end(); iter.move())
    potential += iter.getEdge().residualCapacity();

  return potential;
}

template <class Edge>
inline typename Edge::FlowType
getPotential(const Net<Edge> &net, const typename Edge::IndexType &vertex,
             const vector<typename Edge::FlowType> &innerPotential,
             const vector<typename Edge::FlowType> &outerPotential) {
  if (vertex == net.source)
    return outerPotential[vertex];

  else if (vertex == net.sink)
    return innerPotential[vertex];

  else
    return min<typename Edge::FlowType>(outerPotential[vertex],
                                        innerPotential[vertex]);
}

template <class Edge>
inline void deleteVertexOneSide(const Net<Edge> &layeredNet,
                                typename Net<Edge>::EdgeIterator iter,
                                vector<typename Edge::FlowType> &innerPotential,
                                vector<typename Edge::FlowType> &outerPotential,
                                vector<bool> &isDeleted) {
  for (iter.begin(); !iter.end(); iter.move()) {
    Edge edge = iter.getEdge();

    if (edge.capacity == 0)
      continue;

    typename Edge::IndexType nextVertex =
        (iter.getIteratorType() == Net<Edge>::EdgeIterator::IteratorType::outer
             ? edge.to
             : edge.from);
    (iter.getIteratorType() == Net<Edge>::EdgeIterator::IteratorType::outer
         ? innerPotential[nextVertex]
         : outerPotential[nextVertex]) -= edge.residualCapacity();

    if (getPotential(layeredNet, nextVertex, innerPotential, outerPotential) ==
        0)
      deleteVertex(layeredNet, nextVertex, innerPotential, outerPotential,
                   isDeleted);
  }
}

template <class Edge>
void deleteVertex(const Net<Edge> &layeredNet,
                  const typename Edge::IndexType &vertex,
                  vector<typename Edge::FlowType> &innerPotential,
                  vector<typename Edge::FlowType> &outerPotential,
                  vector<bool> &isDeleted) {
  if (isDeleted[vertex])
    return;

  isDeleted[vertex] = true;
  deleteVertexOneSide<Edge>(layeredNet,
                            layeredNet.getConstOuterEdgeIterator(vertex),
                            innerPotential, outerPotential, isDeleted);
  deleteVertexOneSide<Edge>(layeredNet,
                            layeredNet.getConstInnerEdgeIterator(vertex),
                            innerPotential, outerPotential, isDeleted);
}

template <typename Edge>
void pushFlowFromRoot(Net<Edge> &layeredNet,
                      const typename Edge::IndexType &root,
                      const typename Edge::FlowType &pushingFlow,
                      const typename Edge::IndexType &destination,
                      vector<typename Edge::FlowType> &innerPotential,
                      vector<typename Edge::FlowType> &outerPotential,
                      const vector<bool> &isDeleted) {
  // BFS init:
  queue<typename Edge::IndexType> verticesQueue;
  vector<bool> used(layeredNet.getVerticesCount(), false);
  verticesQueue.push(root);
  used[root] = true;

  // Other data init:
  vector<typename Edge::FlowType> excessOrLack(layeredNet.getVerticesCount(),
                                               0);
  excessOrLack[root] = pushingFlow;

  // BFS:
  while (!verticesQueue.empty()) {
    typename Edge::IndexType vertex = verticesQueue.front();
    verticesQueue.pop();

    if (vertex == destination)
      break;

    for (typename Net<Edge>::EdgeIterator &iter =
             (destination == layeredNet.sink
                  ? layeredNet.getOuterEdgeIterator(vertex)
                  : layeredNet.getInnerEdgeIterator(vertex));
         !iter.end(); iter.move()) {
      Edge edge = iter.getEdge();
      typename Edge::IndexType nextVertex =
          (destination == layeredNet.sink ? edge.to : edge.from);

      if (edge.capacity > 0 && !isDeleted[nextVertex]) {
        if (!used[nextVertex]) {
          verticesQueue.push(nextVertex);
          used[nextVertex] = true;
        }

        typename Edge::FlowType pushedFlow = min<typename Edge::FlowType>(
            excessOrLack[vertex], edge.residualCapacity());
        excessOrLack[vertex] -= pushedFlow;
        excessOrLack[nextVertex] += pushedFlow;
        iter.increaseFlow(pushedFlow);
        outerPotential[edge.from] -= pushedFlow;
        innerPotential[edge.to] -= pushedFlow;
      }

      if (excessOrLack[vertex] == 0)
        break;
    }
  }
}

template <class Edge>
void setBlockingFlowWithMalhotraKumarMaheshwari(Net<Edge> &layeredNet) {
  // Initialize potentials:
  vector<typename Edge::FlowType> innerPotential(layeredNet.getVerticesCount());
  vector<typename Edge::FlowType> outerPotential(layeredNet.getVerticesCount());

  for (typename Edge::IndexType vertex = 0;
       vertex < layeredNet.getVerticesCount(); vertex++) {
    innerPotential[vertex] =
        setPotentialOneSide<Edge>(layeredNet.getConstInnerEdgeIterator(vertex));
    outerPotential[vertex] =
        setPotentialOneSide<Edge>(layeredNet.getConstOuterEdgeIterator(vertex));
  }

  // Initialize deleted vertices:
  vector<bool> isDeleted(layeredNet.getVerticesCount(), false);

  // Main cycle:
  while (true) {
    // Deleting traverse:
    for (typename Edge::IndexType vertex = 0;
         vertex < layeredNet.getVerticesCount(); vertex++)
      if (!isDeleted[vertex] &&
          getPotential(layeredNet, vertex, innerPotential, outerPotential) == 0)
        deleteVertex(layeredNet, vertex, innerPotential, outerPotential,
                     isDeleted);

    if (isDeleted[layeredNet.source] || isDeleted[layeredNet.sink])
      break;

    // Finding root:
    typename Edge::IndexType root = layeredNet.source;

    for (typename Edge::IndexType vertex = 0;
         vertex < layeredNet.getVerticesCount(); vertex++)
      if (!isDeleted[vertex] &&
          getPotential(layeredNet, vertex, innerPotential, outerPotential) <=
              getPotential(layeredNet, root, innerPotential, outerPotential))
        root = vertex;

    typename Edge::FlowType rootPotential =
        getPotential(layeredNet, root, innerPotential, outerPotential);

    // Pushing flow through the root:
    pushFlowFromRoot(layeredNet, root, rootPotential, layeredNet.sink,
                     innerPotential, outerPotential, isDeleted);
    pushFlowFromRoot(layeredNet, root, rootPotential, layeredNet.source,
                     innerPotential, outerPotential, isDeleted);
  }
}

// Global Max Flow augmenting paths algorithm:
template <class Edge> Net<Edge> buildLayeredNetwork(const Net<Edge> &net) {
  // BFS init:
  queue<typename Edge::IndexType> verticesQueue;
  vector<bool> used(net.getVerticesCount(), false);
  verticesQueue.push(net.source);

  // Layered Net init:
  Net<Edge> layeredNet(net.getVerticesCount());
  layeredNet.source = net.source;
  layeredNet.sink = net.sink;
  vector<typename Edge::IndexType> layers(
      net.getVerticesCount(), numeric_limits<typename Edge::IndexType>::max());
  layers[net.source] = 0;

  // BFS:
  while (!verticesQueue.empty()) {
    typename Edge::IndexType vertex = verticesQueue.front();
    verticesQueue.pop();

    if (used[vertex])
      continue;

    used[vertex] = true;

    typename Net<Edge>::EdgeIterator iter =
        net.getConstOuterEdgeIterator(vertex);

    for (iter.begin(); !iter.end(); iter.move()) {
      Edge edge = iter.getEdge();

      if (edge.residualCapacity() > 0 &&
          layers[edge.from] + 1 <= layers[edge.to]) {
        verticesQueue.push(edge.to);

        Edge residualEdge = edge;
        residualEdge.capacity = edge.residualCapacity();
        residualEdge.flow = 0;
        layeredNet.addEdge(residualEdge);
        layers[edge.to] = layers[edge.from] + 1;
      }
    }
  }

  return layeredNet;
}

// Класс bfs iterator, который будет делать все логику:
template <class Edge>
void transferFlowFromLayeredNetworkToNetwork(Net<Edge> &layeredNet,
                                             Net<Edge> &net) {
  // BFS init:
  queue<typename Edge::IndexType> verticesQueue;
  vector<bool> used(net.getVerticesCount(), false);
  verticesQueue.push(net.source);

  // Layered Net init:
  vector<typename Edge::IndexType> layers(
      net.getVerticesCount(), numeric_limits<typename Edge::IndexType>::max());
  layers[net.source] = 0;

  // BFS:
  while (!verticesQueue.empty()) {
    typename Edge::IndexType vertex = verticesQueue.front();
    verticesQueue.pop();

    if (used[vertex])
      continue;

    used[vertex] = true;

    typename Net<Edge>::EdgeIterator iter =
        net.getConstOuterEdgeIterator(vertex);
    typename Net<Edge>::EdgeIterator &layeredNetIter =
        layeredNet.getOuterEdgeIterator(vertex);
    layeredNetIter.begin();

    for (iter.begin(); !iter.end() && !layeredNetIter.end(); iter.move()) {
      Edge edge = iter.getEdge();

      if (edge.residualCapacity() > 0 &&
          layers[edge.from] + 1 <= layers[edge.to]) {
        verticesQueue.push(edge.to);

        layers[edge.to] = layers[edge.from] + 1;

        while (layeredNetIter.getEdge().capacity == 0)
          layeredNetIter.move();

        iter.increaseFlow(layeredNetIter.getEdge().flow);
        layeredNetIter.move();
      }
    }
  }
}

// Сделать классом с кастомным виртуальным blocking flow:
template <class Edge> void setMaxFlowWithAugmentingPaths(Net<Edge> &net) {
  while (true) {
    Net<Edge> layeredNet = buildLayeredNetwork(net);
    setBlockingFlowWithMalhotraKumarMaheshwari(layeredNet);

    if (getFlowWithCheck(layeredNet) == 0)
      break;

    else {
      transferFlowFromLayeredNetworkToNetwork(layeredNet, net);
    }
  }
}

// --------------------------------------------------

// My custom Edge:
template <typename FirstType = unsigned, typename SecondType = long long>
struct Edge {
  typedef FirstType IndexType;
  typedef SecondType FlowType;
  IndexType from;
  IndexType to;
  FlowType flow;
  FlowType capacity;

  Edge(const IndexType &from, const IndexType &to, const FlowType &capacity) {
    this->from = from;
    this->to = to;
    this->flow = 0;
    this->capacity = capacity;
  }

  FlowType residualCapacity() const { return capacity - flow; }

  Edge reversed() const { return Edge(to, from, 0); }
};

// Custom inputs/outputs:
template <class Edge> void printEdge(const Edge &edge, ostream &os = cout) {
  os << edge.from << " -> " << edge.to << " (" << edge.flow << "/"
     << edge.capacity << ")";
}

template <class Edge> void printNet(Net<Edge> &net, ostream &os = cout) {
  for (typename Edge::IndexType vertex = 0; vertex < net.getVerticesCount();
       vertex++) {
    typename Net<Edge>::EdgeIterator iter =
        net.getConstOuterEdgeIterator(vertex);

    for (iter.begin(); !iter.end(); iter.move()) {
      printEdge(iter.getEdge(), os);
      os << " ";
    }

    os << endl;
  }
}

/*
// Сделать нормальный input.
long long solve () {
        unsigned verticesCount;
        cin >> verticesCount;
        const long long maxCapacity = verticesCount * 1000 + 1;
        long long positiveSum = 0;

        Net<Edge<unsigned, long long> > net(verticesCount + 2);
        net.source = verticesCount;
        net.sink = verticesCount + 1;

        for (unsigned i = 0; i < verticesCount; i ++) {
                long long usability;
                cin >> usability;

                if (usability > 0) {
                        positiveSum += usability;
                        net.addEdge(Edge<unsigned, long long>(net.source, i,
usability));
                }

                else
                        net.addEdge(Edge<unsigned, long long>(i, net.sink, -
usability));
        }

        for (unsigned from = 0; from < verticesCount; from ++) {
                unsigned nextEdgesCount;
                cin >> nextEdgesCount;

                for (unsigned edge = 0; edge < nextEdgesCount; edge ++) {
                        unsigned to;
                        cin >> to;
                        net.addEdge(Edge<unsigned, long long>(from, to - 1,
maxCapacity));
                }
        }

        setMaxFlowWithPreflowPush(net);
        return positiveSum - getFlowWithCheck(net);
}
*/

int main() {
  unsigned verticesCount, edgesCount;
  cin >> verticesCount >> edgesCount;

  Net<Edge<unsigned, long long>> net(verticesCount);
  net.source = 0;
  net.sink = verticesCount - 1;

  for (unsigned i = 0; i < edgesCount; i++) {
    unsigned from, to;
    long long capacity;
    cin >> from >> to >> capacity;
    net.addEdge(Edge<unsigned, long long>(from - 1, to - 1, capacity));
  }

  setMaxFlowWithAugmentingPaths(net);
  cout << getFlowWithCheck(net) << endl;

  return 0;
}