Problem p02376 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>

using namespace std;
const int maxN = 3e2 + 100;
int n, m, st, fn;
int cap[maxN][maxN], excess[maxN], height[maxN];
vector<int> g[maxN];
set<pair<int, int>> candidates;

void input() {
  cin >> n >> m;
  // cin>>st>>fn;
  st = 1;
  fn = n;
  for (int i = 1; i <= m; i++) {
    int k1, k2, val;
    cin >> k1 >> k2 >> val;
    k1++;
    k2++;
    if (cap[k1][k2] == 0 && cap[k1][k2] == 0) {
      g[k1].push_back(k2);
      g[k2].push_back(k1);
    }
    cap[k1][k2] += val;
  }
}
int findExcessedVertex() {
  while (candidates.size() > 0) {
    auto item = *candidates.begin();
    if (item.second == st || item.second == fn)
      candidates.erase(item);
    else
      return item.second;
  }
  return 0;
}
bool push(int v) // change to multi push
{
  bool done = false;
  for (auto u : g[v])
    if (cap[v][u] > 0 && height[v] >= height[u] + 1) // h[v]==h[u]+1
    {
      int delta = min(excess[v], cap[v][u]);
      cap[v][u] -= delta;
      cap[u][v] += delta;
      excess[v] -= delta;
      if (excess[v] == 0)
        candidates.erase({height[v], v});
      if (excess[u] == 0)
        candidates.insert({height[u], u});
      excess[u] += delta;
      done = true;
      // return done;
    }
  return done;
}
void relabel(int v) {
  height[v]++;
  if (candidates.find({height[v] - 1, v}) != candidates.end()) {
    candidates.erase({height[v] - 1, v});
    candidates.insert({height[v], v});
  }
}
void GT_init() {
  height[st] = n;
  height[fn] = 0; // not done
  for (auto u : g[st])
    if (cap[st][u] > 0) {
      int delta = cap[st][u];
      cap[st][u] -= delta;
      cap[u][st] += delta;
      excess[st] -= delta;
      if (excess[st] == 0)
        candidates.erase({height[st], st});
      if (excess[u] == 0)
        candidates.insert({height[u], u});
      excess[u] += delta;
    }
}
int Goldberg_Tarjan() {
  GT_init();
  while (int v = findExcessedVertex()) {

    // cout<<"gt "<<v<<" "<<excess[v]<<" "<<height[v]<<endl;
    if (!push(v))
      relabel(v);
  }
  return excess[fn];
}
int main() {
  input();
  int Maxflow = Goldberg_Tarjan();
  cout << Maxflow << endl;

  return 0;
}

Fixed submission:
#include <bits/stdc++.h>

using namespace std;
const int maxN = 3e2 + 100;
int n, m, st, fn;
int cap[maxN][maxN], excess[maxN], height[maxN];
vector<int> g[maxN];
set<pair<int, int>> candidates;

void input() {
  cin >> n >> m;
  // cin>>st>>fn;
  st = 1;
  fn = n;
  for (int i = 1; i <= m; i++) {
    int k1, k2, val;
    cin >> k1 >> k2 >> val;
    k1++;
    k2++;
    if (cap[k1][k2] == 0 && cap[k1][k2] == 0) {
      g[k1].push_back(k2);
      g[k2].push_back(k1);
    }
    cap[k1][k2] += val;
  }
}
int findExcessedVertex() {
  while (candidates.size() > 0) {
    auto item = *candidates.begin();
    if (item.second == st || item.second == fn)
      candidates.erase(item);
    else
      return item.second;
  }
  return 0;
}
bool push(int v) // change to multi push
{
  bool done = false;
  for (auto u : g[v])
    if (cap[v][u] > 0 && height[v] >= height[u] + 1) // h[v]==h[u]+1
    {
      int delta = min(excess[v], cap[v][u]);
      cap[v][u] -= delta;
      cap[u][v] += delta;
      excess[v] -= delta;
      if (excess[v] == 0)
        candidates.erase({height[v], v});
      if (excess[u] == 0)
        candidates.insert({height[u], u});
      excess[u] += delta;
      done = true;
      if (excess[v] == 0)
        break;
      // return done;
    }
  return done;
}
void relabel(int v) {
  height[v]++;
  if (candidates.find({height[v] - 1, v}) != candidates.end()) {
    candidates.erase({height[v] - 1, v});
    candidates.insert({height[v], v});
  }
}
void GT_init() {
  height[st] = n;
  height[fn] = 0; // not done
  for (auto u : g[st])
    if (cap[st][u] > 0) {
      int delta = cap[st][u];
      cap[st][u] -= delta;
      cap[u][st] += delta;
      excess[st] -= delta;
      if (excess[st] == 0)
        candidates.erase({height[st], st});
      if (excess[u] == 0)
        candidates.insert({height[u], u});
      excess[u] += delta;
    }
}
int Goldberg_Tarjan() {
  GT_init();
  while (int v = findExcessedVertex()) {

    // cout<<"gt "<<v<<" "<<excess[v]<<" "<<height[v]<<endl;
    if (!push(v))
      relabel(v);
  }
  return excess[fn];
}
int main() {
  input();
  int Maxflow = Goldberg_Tarjan();
  cout << Maxflow << endl;

  return 0;
}