Problem p03837 (C++)

Buggy submission (status: Runtime Error):
#include <algorithm>
#include <bitset>
#include <cassert>
#include <ciso646>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstring>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <utility>
#include <vector>
using namespace std;

typedef long long ll;
typedef unsigned long long ul;
typedef unsigned int ui;
typedef long double ld;
const int inf = 1e+9;
const ll mod = 1000000007;
const ll INF = mod * mod;
#define rep(i, n) for (int i = 0; i < n; i++)
#define per(i, n) for (int i = n - 1; i >= 0; i--)
#define Rep(i, sta, n) for (int i = sta; i < n; i++)
#define rep1(i, n) for (int i = 1; i <= n; i++)
#define per1(i, n) for (int i = n; i >= 1; i--)
#define Rep1(i, sta, n) for (int i = sta; i <= n; i++)
typedef complex<ld> Point;
const ld eps = 1e-8;
const ld pi = acos(-1.0);
typedef pair<int, int> P;
typedef pair<ld, ld> LDP;
typedef pair<ll, ll> LP;
typedef vector<int> vec;
typedef vector<string> svec;
#define fr first
#define sc second
#define all(c) c.begin(), c.end()
#define pb push_back
// #define int long long

void solve() {
  int N, M;
  cin >> N >> M;
  int d[120][120];
  rep(i, N) {
    rep(j, N) { d[i][j] = inf; }
  }
  rep(i, N) d[i][i] = 0;
  int a[1200], b[1200], c[1200];
  rep(i, M) {
    cin >> a[i] >> b[i] >> c[i];
    a[i]--;
    b[i]--;
    d[a[i]][b[i]] = c[i];
    d[b[i]][a[i]] = c[i];
  }
  rep(k, N) {
    rep(i, N) {
      rep(j, N) { d[i][j] = min(d[i][j], d[i][k] + d[k][j]); }
    }
  }
  bool used[120];
  rep(i, M) used[i] = false;
  rep(i, N) {
    rep(j, N) {
      rep(k, M) {
        if (d[i][j] == d[i][a[k]] + c[k] + d[b[k]][j]) {
          used[k] = true;
        }
        if (d[i][j] == d[i][b[k]] + c[k] + d[a[k]][j]) {
          used[k] = true;
        }
      }
    }
  }
  int ans = 0;
  rep(i, M) {
    if (!used[i])
      ans++;
  }
  cout << ans << endl;
}

signed main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  // cout << fixed << setprecision(10);
  // init();
  solve();
  // cout << "finish" << endl;
  return 0;
}

Fixed submission:
#include <algorithm>
#include <bitset>
#include <cassert>
#include <ciso646>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstring>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <utility>
#include <vector>
using namespace std;

typedef long long ll;
typedef unsigned long long ul;
typedef unsigned int ui;
typedef long double ld;
const int inf = 1e+9;
const ll mod = 1000000007;
const ll INF = mod * mod;
#define rep(i, n) for (int i = 0; i < n; i++)
#define per(i, n) for (int i = n - 1; i >= 0; i--)
#define Rep(i, sta, n) for (int i = sta; i < n; i++)
#define rep1(i, n) for (int i = 1; i <= n; i++)
#define per1(i, n) for (int i = n; i >= 1; i--)
#define Rep1(i, sta, n) for (int i = sta; i <= n; i++)
typedef complex<ld> Point;
const ld eps = 1e-8;
const ld pi = acos(-1.0);
typedef pair<int, int> P;
typedef pair<ld, ld> LDP;
typedef pair<ll, ll> LP;
typedef vector<int> vec;
typedef vector<string> svec;
#define fr first
#define sc second
#define all(c) c.begin(), c.end()
#define pb push_back
// #define int long long

void solve() {
  int N, M;
  cin >> N >> M;
  int d[120][120];
  rep(i, N) {
    rep(j, N) { d[i][j] = inf; }
  }
  rep(i, N) d[i][i] = 0;
  int a[1200], b[1200], c[1200];
  rep(i, M) {
    cin >> a[i] >> b[i] >> c[i];
    a[i]--;
    b[i]--;
    d[a[i]][b[i]] = c[i];
    d[b[i]][a[i]] = c[i];
  }
  rep(k, N) {
    rep(i, N) {
      rep(j, N) { d[i][j] = min(d[i][j], d[i][k] + d[k][j]); }
    }
  }
  bool used[1200];
  rep(i, M) used[i] = false;
  rep(i, N) {
    rep(j, N) {
      rep(k, M) {
        if (d[i][j] == d[i][a[k]] + c[k] + d[b[k]][j]) {
          used[k] = true;
        }
        if (d[i][j] == d[i][b[k]] + c[k] + d[a[k]][j]) {
          used[k] = true;
        }
      }
    }
  }
  int ans = 0;
  rep(i, M) {
    if (!used[i])
      ans++;
  }
  cout << ans << endl;
}

signed main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  // cout << fixed << setprecision(10);
  // init();
  solve();
  // cout << "finish" << endl;
  return 0;
}