Problem p03837 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (ll i = 0; i < n; i++)
#define repl(i, l, r) for (ll i = (l); i < (r); i++)
#define per(i, n) for (ll i = n - 1; i >= 0; i--)
#define perl(i, r, l) for (ll i = r - 1; i >= l; i--)
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define ins insert
#define pqueue(x) priority_queue<x, vector<x>, greater<x>>
#define all(x) (x).begin(), (x).end()
#define CST(x) cout << fixed << setprecision(x)
#define vtpl(x, y, z) vector<tuple<x, y, z>>
#define rev(x) reverse(x);
using ll = long long;
using vl = vector<ll>;
using vvl = vector<vector<ll>>;
using pl = pair<ll, ll>;
using vpl = vector<pl>;
using vvpl = vector<vpl>;
const ll MOD = 1000000007;
const ll MOD9 = 998244353;
const int inf = 1e9 + 10;
const ll INF = 4e18;
const ll dy[8] = {1, 0, -1, 0, 1, 1, -1, -1};
const ll dx[8] = {0, -1, 0, 1, 1, -1, 1, -1};
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
int main() {
  ll n, m;
  cin >> n >> m;
  vvl v(n, vl(n, inf));
  vpl p(n);
  vl w(n);
  rep(i, n) v[i][i] = 0;
  rep(i, m) {
    ll a, b, c;
    cin >> a >> b >> c;
    a--;
    b--;
    v[a][b] = c;
    v[b][a] = c;
    p[i].fi = a;
    p[i].se = b;
    w[i] = c;
  }
  rep(k, n) rep(i, n) rep(j, n) chmin(v[i][j], v[i][k] + v[k][j]);
  ll ans = 0;
  rep(i, m) {
    ll x = p[i].fi, y = p[i].se, c = w[i];
    if (v[x][y] != c)
      ans++;
  }
  cout << ans << endl;
}

Fixed submission:
#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (ll i = 0; i < n; i++)
#define repl(i, l, r) for (ll i = (l); i < (r); i++)
#define per(i, n) for (ll i = n - 1; i >= 0; i--)
#define perl(i, r, l) for (ll i = r - 1; i >= l; i--)
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define ins insert
#define pqueue(x) priority_queue<x, vector<x>, greater<x>>
#define all(x) (x).begin(), (x).end()
#define CST(x) cout << fixed << setprecision(x)
#define vtpl(x, y, z) vector<tuple<x, y, z>>
#define rev(x) reverse(x);
using ll = long long;
using vl = vector<ll>;
using vvl = vector<vector<ll>>;
using pl = pair<ll, ll>;
using vpl = vector<pl>;
using vvpl = vector<vpl>;
const ll MOD = 1000000007;
const ll MOD9 = 998244353;
const int inf = 1e9 + 10;
const ll INF = 4e18;
const ll dy[8] = {1, 0, -1, 0, 1, 1, -1, -1};
const ll dx[8] = {0, -1, 0, 1, 1, -1, 1, -1};
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
int main() {
  ll n, m;
  cin >> n >> m;
  vvl v(n, vl(n, inf));
  vpl p(m);
  vl w(m);
  rep(i, n) v[i][i] = 0;
  rep(i, m) {
    ll a, b, c;
    cin >> a >> b >> c;
    a--;
    b--;
    v[a][b] = c;
    v[b][a] = c;
    p[i].fi = a;
    p[i].se = b;
    w[i] = c;
  }
  rep(k, n) rep(i, n) rep(j, n) chmin(v[i][j], v[i][k] + v[k][j]);
  ll ans = 0;
  rep(i, m) {
    ll x = p[i].fi, y = p[i].se, c = w[i];
    if (v[x][y] != c)
      ans++;
  }
  cout << ans << endl;
}