Problem p02689 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define rep(i, n) for (int i = 0; i < (n); i++)
#define rep2(i, n) for (int i = 1; i <= (n); i++)
#define rep3(i, i0, n) for (int i = i0; i < (n); i++)
#define pb push_back
#define mod 1000000007
#define INF 200000000000
template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> bool chmin(T &a, const T &b) {
  if (b < a) {
    a = b;
    return 1;
  }
  return 0;
}
ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }
#define all(x) x.begin(), x.end()

bool compare(pair<int, int> a, pair<int, int> b) {
  if (a.first != b.first) {
    return a.first < b.first;

  } else {
    return a.second < b.second;
  }
}
// 入力

vector<vector<ll>> G;
vector<bool> seen;
vector<ll> h;

ll cnt = 1;
ll mx;
ll flag;
// ll fcnt=1;
void dfs(ll v) {
  seen[v] = 1;
  if (h[v] == mx) {
    flag = 1;
  }
  if (h[v] > mx) {
    mx = h[v];
    flag = 0;
  }
  rep(i, G[v].size()) {
    if (seen[G[v][i]] == 0) {
      dfs(G[v][i]);
    }
  }
}

int main() {
  ll n, m;
  cin >> n >> m;
  G.resize(n);
  seen.resize(n);
  h.resize(n);

  rep(i, n) { cin >> h[i]; }

  rep(i, m) {
    ll a, b;
    cin >> a >> b;
    a--;
    b--;
    G[a].pb(b);
    G[b].pb(a);
  }

  ll ans = 0;
  vector<ll> an(n);
  rep(k, n) {

    if (an[k] == 0) {
      vector<ll> dist(n, -1);
      queue<ll> que;
      dist[k] = 0;
      que.push(k);
      while (!que.empty()) {
        ll v = que.front();
        que.pop();
        flag = 0;
        for (ll i : G[v]) {
          if (h[v] == h[i]) {
            an[v] = 1;
            an[i] = 1;
            break;
          } else if (h[v] < h[i]) {
            an[v] = 1;
            break;
          } else {
            an[i] = 1;
          }
        }
      }
    }
  }

  rep(i, n) {
    if (an[i] == 0) {
      ans++;
    }
  }
  cout << ans << endl;

  return 0;
}

Fixed submission:
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define rep(i, n) for (int i = 0; i < (n); i++)
#define rep2(i, n) for (int i = 1; i <= (n); i++)
#define rep3(i, i0, n) for (int i = i0; i < (n); i++)
#define pb push_back
#define mod 1000000007
#define INF 200000000000
template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> bool chmin(T &a, const T &b) {
  if (b < a) {
    a = b;
    return 1;
  }
  return 0;
}
ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }
#define all(x) x.begin(), x.end()

bool compare(pair<int, int> a, pair<int, int> b) {
  if (a.first != b.first) {
    return a.first < b.first;

  } else {
    return a.second < b.second;
  }
}
// 入力

vector<vector<ll>> G;
vector<bool> seen;
vector<ll> h;

ll cnt = 1;
ll mx;
ll flag;
// ll fcnt=1;
void dfs(ll v) {
  seen[v] = 1;
  if (h[v] == mx) {
    flag = 1;
  }
  if (h[v] > mx) {
    mx = h[v];
    flag = 0;
  }
  rep(i, G[v].size()) {
    if (seen[G[v][i]] == 0) {
      dfs(G[v][i]);
    }
  }
}

int main() {
  ll n, m;
  cin >> n >> m;
  G.resize(n);
  seen.resize(n);
  h.resize(n);

  rep(i, n) { cin >> h[i]; }

  rep(i, m) {
    ll a, b;
    cin >> a >> b;
    a--;
    b--;
    G[a].pb(b);
    G[b].pb(a);
  }

  ll ans = 0;
  vector<ll> an(n);
  rep(k, n) {

    if (an[k] == 0) {

      for (ll i : G[k]) {
        if (h[k] == h[i]) {
          an[k] = 1;
          an[i] = 1;
          break;
        } else if (h[k] < h[i]) {
          an[k] = 1;
          break;
        } else {
          an[i] = 1;
        }
      }
    }
  }

  rep(i, n) {
    if (an[i] == 0) {
      ans++;
    }
  }
  cout << ans << endl;

  return 0;
}