Problem p03452 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <algorithm>
#include <bitset>
#include <cmath>
#include <complex>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <utility>
#include <vector>
using namespace std;
using LL = long long;
using ULL = unsigned long long;
typedef pair<LL, LL> P;
constexpr int INF = 2000000000;
constexpr int HINF = INF / 2;
constexpr double DINF = 100000000000000000.0;
constexpr long long LINF = 9223372036854775807;
constexpr long long HLINF = 4500000000000000000;
constexpr long long MMOD = 500000004;
const double PI = acos(-1);
int dx[4] = {0, 1, 0, -1}, dy[4] = {1, 0, -1, 0};
#define ALL(x) (x).begin(), (x).end()
#define UNIQ(c) (c).erase(unique(ALL((c))), end((c)))
#define mp make_pair
#define eb emplace_back
#define FOR(i, a, b) for (int i = (a); i < (b); i++)
#define RFOR(i, a, b) for (int i = (a); i >= (b); i--)
#define REP(i, n) FOR(i, 0, n)
#define INIT                                                                   \
  std::ios::sync_with_stdio(false);                                            \
  std::cin.tie(0)

vector<pair<int, LL>> G[101010];

LL l[202020], r[202020], d[202020];
bool used[101010];
LL pos[101010];
int n, m;

bool serch(int p) {
  queue<int> q;
  q.push(p);

  while (!q.empty()) {
    int Pos = q.front();
    q.pop();
    used[Pos] = true;
    REP(i, G[Pos].size()) {
      if (!used[G[Pos][i].first]) {
        q.push(G[Pos][i].first);
        pos[G[Pos][i].first] = pos[Pos] + G[Pos][i].second;
      } else {
        if (pos[Pos] + G[Pos][i].second != pos[G[Pos][i].first])
          return false;
      }
    }
  }
  return true;
}

int main() {
  cin >> n >> m;
  int first;
  REP(i, m) {
    cin >> l[i] >> r[i] >> d[i];
    l[i]--, r[i]--;
    if (!i)
      first = l[i];
    G[r[i]].emplace_back(mp(l[i], d[i]));
    G[l[i]].emplace_back(mp(r[i], -d[i]));
  }
  REP(i, n) pos[i] = LINF;
  REP(i, n) {
    if (!used[i]) {
      pos[i] = 0;
      if (serch(i) == false) {
        cout << "No" << endl;
        return 0;
      }
    }
  }
  cout << "Yes" << endl;
}

Fixed submission:
#include <algorithm>
#include <bitset>
#include <cmath>
#include <complex>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <utility>
#include <vector>
using namespace std;
using LL = long long;
using ULL = unsigned long long;
typedef pair<LL, LL> P;
constexpr int INF = 2000000000;
constexpr int HINF = INF / 2;
constexpr double DINF = 100000000000000000.0;
constexpr long long LINF = 9223372036854775807;
constexpr long long HLINF = 4500000000000000000;
constexpr long long MMOD = 500000004;
const double PI = acos(-1);
int dx[4] = {0, 1, 0, -1}, dy[4] = {1, 0, -1, 0};
#define ALL(x) (x).begin(), (x).end()
#define UNIQ(c) (c).erase(unique(ALL((c))), end((c)))
#define mp make_pair
#define eb emplace_back
#define FOR(i, a, b) for (int i = (a); i < (b); i++)
#define RFOR(i, a, b) for (int i = (a); i >= (b); i--)
#define REP(i, n) FOR(i, 0, n)
#define INIT                                                                   \
  std::ios::sync_with_stdio(false);                                            \
  std::cin.tie(0)

vector<pair<int, LL>> G[101010];

LL l[202020], r[202020], d[202020];
bool used[101010];
LL pos[101010];
int n, m;

bool serch(int p) {
  queue<int> q;
  q.push(p);

  while (!q.empty()) {
    int Pos = q.front();
    q.pop();
    used[Pos] = true;
    REP(i, G[Pos].size()) {
      if (!used[G[Pos][i].first]) {
        q.push(G[Pos][i].first);
        used[G[Pos][i].first] = true;
        pos[G[Pos][i].first] = pos[Pos] + G[Pos][i].second;
      } else {
        if (pos[Pos] + G[Pos][i].second != pos[G[Pos][i].first])
          return false;
      }
    }
  }
  return true;
}

int main() {
  cin >> n >> m;
  int first;
  REP(i, m) {
    cin >> l[i] >> r[i] >> d[i];
    l[i]--, r[i]--;
    if (!i)
      first = l[i];
    G[r[i]].emplace_back(mp(l[i], d[i]));
    G[l[i]].emplace_back(mp(r[i], -d[i]));
  }
  REP(i, n) pos[i] = LINF;
  REP(i, n) {
    if (!used[i]) {
      pos[i] = 0;
      if (serch(i) == false) {
        cout << "No" << endl;
        return 0;
      }
    }
  }
  cout << "Yes" << endl;
}