Problem p03450 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
using namespace std;

// #define int long long
#define rep(i, n) for (int i = (int)(0); i < (int)(n); ++i)
#define reps(i, n) for (int i = (int)(1); i <= (int)(n); ++i)
#define rrep(i, n) for (int i = ((int)(n)-1); i >= 0; i--)
#define rreps(i, n) for (int i = ((int)(n)); i > 0; i--)
#define irep(i, m, n) for (int i = (int)(m); i < (int)(n); ++i)
#define ireps(i, m, n) for (int i = (int)(m); i <= (int)(n); ++i)
#define SORT(v, n) sort(v, v + n);
#define REVERSE(v, n) reverse(v, v + n);
#define vsort(v) sort(v.begin(), v.end());
#define all(v) v.begin(), v.end()
#define mp(n, m) make_pair(n, m);
#define cout(d) cout << d << endl;
#define coutd(d) cout << std::setprecision(10) << d << endl;
#define cinline(n) getline(cin, n);
#define replace_all(s, b, a) replace(s.begin(), s.end(), b, a);
#define PI (acos(-1))
#define FILL(v, n, x) fill(v, v + n, x);
#define sz(x) int(x.size())

using ll = long long;
using vi = vector<int>;
using vvi = vector<vi>;
using vll = vector<ll>;
using vvll = vector<vll>;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using vs = vector<string>;
using vpll = vector<pair<ll, ll>>;

template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}

const ll INF = 1e15;
const int MOD = 1e9 + 7;
const ll LINF = 1e18;

ll n, m;
vpll G[1000005];
ll dist[1000005];
bool visited[1000005];

void dfs(ll v) {
  visited[v] = true;
  for (auto np : G[v]) {
    ll nv = np.first, nc = np.second;
    if (dist[nv] != -1) {
      if (dist[nv] != dist[v] + nc) {
        // cout<<v<<" "<<nv<<" "<<nc<<" "<<dist[v]<<" "<<dist[nv]<<endl;
        cout << "No" << endl;
        exit(0);
      }
    } else {
      dist[nv] = dist[v] + nc;
      dfs(nv);
    }
  }
}

signed main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cin >> n >> m;
  rep(i, m) {
    ll a, b, c;
    cin >> a >> b >> c;
    a--, b--;
    G[a].emplace_back(b, c);
    G[b].emplace_back(a, -c);
  }
  memset(dist, -1, sizeof(dist));
  rep(i, n) {
    // cout<<i<<endl;
    if (visited[i])
      continue;
    dist[i] = 0;
    dfs(i);
  }
  cout << "Yes" << endl;
}

Fixed submission:
#include <bits/stdc++.h>
using namespace std;

// #define int long long
#define rep(i, n) for (int i = (int)(0); i < (int)(n); ++i)
#define reps(i, n) for (int i = (int)(1); i <= (int)(n); ++i)
#define rrep(i, n) for (int i = ((int)(n)-1); i >= 0; i--)
#define rreps(i, n) for (int i = ((int)(n)); i > 0; i--)
#define irep(i, m, n) for (int i = (int)(m); i < (int)(n); ++i)
#define ireps(i, m, n) for (int i = (int)(m); i <= (int)(n); ++i)
#define SORT(v, n) sort(v, v + n);
#define REVERSE(v, n) reverse(v, v + n);
#define vsort(v) sort(v.begin(), v.end());
#define all(v) v.begin(), v.end()
#define mp(n, m) make_pair(n, m);
#define cout(d) cout << d << endl;
#define coutd(d) cout << std::setprecision(10) << d << endl;
#define cinline(n) getline(cin, n);
#define replace_all(s, b, a) replace(s.begin(), s.end(), b, a);
#define PI (acos(-1))
#define FILL(v, n, x) fill(v, v + n, x);
#define sz(x) int(x.size())

using ll = long long;
using vi = vector<int>;
using vvi = vector<vi>;
using vll = vector<ll>;
using vvll = vector<vll>;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using vs = vector<string>;
using vpll = vector<pair<ll, ll>>;

template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}

const ll INF = 1e15;
const int MOD = 1e9 + 7;
const ll LINF = 1e18;

ll n, m;
vpll G[1000005];
ll dist[1000005];
bool visited[1000005];

void dfs(ll v) {
  visited[v] = true;
  for (auto np : G[v]) {
    ll nv = np.first, nc = np.second;
    if (visited[nv]) {
      if (dist[nv] != dist[v] + nc) {
        // cout<<v<<" "<<nv<<" "<<nc<<" "<<dist[v]<<" "<<dist[nv]<<endl;
        cout << "No" << endl;
        exit(0);
      }
    } else {
      dist[nv] = dist[v] + nc;
      dfs(nv);
    }
  }
}

signed main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cin >> n >> m;
  rep(i, m) {
    ll a, b, c;
    cin >> a >> b >> c;
    a--, b--;
    G[a].emplace_back(b, c);
    G[b].emplace_back(a, -c);
  }
  memset(dist, -1, sizeof(dist));
  rep(i, n) {
    // cout<<i<<endl;
    if (visited[i])
      continue;
    dist[i] = 0;
    dfs(i);
  }
  cout << "Yes" << endl;
}