Problem p03450 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> P;
typedef pair<int, int> Pi;
#define rep(i, n) for (ll i = 0; i < n; i++)
#define FOR(i, a, b) for (ll i = a; i < b; i++)
#define fi first
#define se second
#define endl "\n"

template <typename T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <typename T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <typename T> ostream &operator<<(ostream &s, const complex<T> &d) {
  return s << "(" << d.real() << ", " << d.imag() << ")";
}
template <typename T1, typename T2>
ostream &operator<<(ostream &s, const pair<T1, T2> &d) {
  return s << "(" << d.first << ", " << d.second << ")";
}
template <typename T> ostream &operator<<(ostream &s, const vector<T> &d) {
  int len = d.size();
  rep(i, len) {
    s << d[i];
    if (i < len - 1)
      s << " ";
  }
  return s;
}
template <typename T>
ostream &operator<<(ostream &s, const vector<vector<T>> &d) {
  int len = d.size();
  rep(i, len) { s << d[i] << endl; }
  return s;
}
template <typename T> ostream &operator<<(ostream &s, const set<T> &v) {
  s << "{ ";
  for (auto itr = v.begin(); itr != v.end(); ++itr) {
    if (itr != v.begin()) {
      s << ", ";
    }
    s << (*itr);
  }
  s << " }";
  return s;
}
template <typename T1, typename T2>
ostream &operator<<(ostream &s, const map<T1, T2> &m) {
  s << "{" << endl;
  for (auto itr = m.begin(); itr != m.end(); ++itr) {
    s << " " << (*itr).first << " : " << (*itr).second << endl;
  }
  s << "}" << endl;
  return s;
}

const ll mod = 1e9 + 7;
const ll inf = 1e17;
const int INF = 1e9;
const double PI = acos(-1);
const double EPS = 1e-10;

struct edge {
  int to, cost;
};

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  int n, m;
  cin >> n >> m;
  vector<vector<edge>> g(n);
  vector<int> l(m), r(m), d(m);
  rep(i, m) {
    cin >> l[i] >> r[i] >> d[i];
    l[i]--, r[i]--;
    g[l[i]].push_back({r[i], d[i]});
    g[r[i]].push_back({l[i], -d[i]});
  }
  vector<int> ans(n, -INF);
  int id = 0;
  auto bfs = [&](int v) {
    queue<int> que;
    que.push(v);
    while (!que.empty()) {
      int from = que.front();
      que.pop();
      for (auto to : g[from]) {
        if (ans[to.to] != -INF)
          continue;
        ans[to.to] = ans[from] + to.cost;
        que.push(to.to);
      }
    }
  };
  rep(i, n) {
    if (ans[i] == -INF) {
      bfs(i);
    }
  }
  rep(i, m) {
    if (ans[r[i]] - ans[l[i]] != d[i]) {
      cout << "No" << endl;
      return 0;
    }
  }
  cout << "Yes" << endl;
}

Fixed submission:
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> P;
typedef pair<int, int> Pi;
#define rep(i, n) for (ll i = 0; i < n; i++)
#define FOR(i, a, b) for (ll i = a; i < b; i++)
#define fi first
#define se second
#define endl "\n"

template <typename T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <typename T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <typename T> ostream &operator<<(ostream &s, const complex<T> &d) {
  return s << "(" << d.real() << ", " << d.imag() << ")";
}
template <typename T1, typename T2>
ostream &operator<<(ostream &s, const pair<T1, T2> &d) {
  return s << "(" << d.first << ", " << d.second << ")";
}
template <typename T> ostream &operator<<(ostream &s, const vector<T> &d) {
  int len = d.size();
  rep(i, len) {
    s << d[i];
    if (i < len - 1)
      s << " ";
  }
  return s;
}
template <typename T>
ostream &operator<<(ostream &s, const vector<vector<T>> &d) {
  int len = d.size();
  rep(i, len) { s << d[i] << endl; }
  return s;
}
template <typename T> ostream &operator<<(ostream &s, const set<T> &v) {
  s << "{ ";
  for (auto itr = v.begin(); itr != v.end(); ++itr) {
    if (itr != v.begin()) {
      s << ", ";
    }
    s << (*itr);
  }
  s << " }";
  return s;
}
template <typename T1, typename T2>
ostream &operator<<(ostream &s, const map<T1, T2> &m) {
  s << "{" << endl;
  for (auto itr = m.begin(); itr != m.end(); ++itr) {
    s << " " << (*itr).first << " : " << (*itr).second << endl;
  }
  s << "}" << endl;
  return s;
}

const ll mod = 1e9 + 7;
const ll inf = 1e17;
const int INF = 1e9;
const double PI = acos(-1);
const double EPS = 1e-10;

struct edge {
  int to, cost;
};

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  int n, m;
  cin >> n >> m;
  vector<vector<edge>> g(n);
  vector<int> l(m), r(m), d(m);
  rep(i, m) {
    cin >> l[i] >> r[i] >> d[i];
    l[i]--, r[i]--;
    g[l[i]].push_back({r[i], d[i]});
    g[r[i]].push_back({l[i], -d[i]});
  }
  vector<int> ans(n, -INF);
  int id = 0;
  auto bfs = [&](int v) {
    queue<int> que;
    que.push(v);
    ans[v] = 0;
    while (!que.empty()) {
      int from = que.front();
      que.pop();
      for (auto to : g[from]) {
        if (ans[to.to] != -INF)
          continue;
        ans[to.to] = ans[from] + to.cost;
        que.push(to.to);
      }
    }
  };
  rep(i, n) {
    if (ans[i] == -INF) {
      bfs(i);
    }
  }
  rep(i, m) {
    if (ans[r[i]] - ans[l[i]] != d[i]) {
      cout << "No" << endl;
      return 0;
    }
  }
  cout << "Yes" << endl;
}