Tunnels

input/code.cpp: In function 'void dfs(int)':
input/code.cpp:16:9: warning: unused variable 't' [-Wunused-variable]
     int t = 0;
         ^

#include<bits/stdc++.h>

#define F first
#define S second
#define ll long long
#define ull unsigned long long
#define pb push_back
using namespace std;
vector < int > g[200000];
int ans, b[200000], used[200000];
set < int > s;
vector < int > k;
void dfs(int v)
{
    used[v] = 1;
    int t = 0;
    for (auto u: g[v])
    if (!used[u]){
        dfs(u);
        break;
    }
    for (auto u: g[v]){
        b[u]--;
        if (b[u] == 0) s.insert(u);
    }
}
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int n, m;
    cin >> n >> m;
    for (int i = 0; i < m; i++){
        int u, v;
        cin >> u >> v;
        g[u].pb(v);
        b[v]++;
    }
    for (int i = 1; i <= n; i++) if (b[i] == 0) k.pb(i);
    for (int i = 1; i <= n; i++){
        for (auto u: k)
        if (!used[u]){
            ans++;
            dfs(u);
        }
        k.clear();
        for (int i: s)
            k.pb(i);
        s.clear();
    }
    cout << ans;
}

Test 1

Group: 1

Verdict: WRONG ANSWER

Test 2

Group: 1

Verdict: WRONG ANSWER

Test 3

Group: 1

Verdict: WRONG ANSWER

Test 4

Group: 1

Verdict: WRONG ANSWER

Test 5

Group: 1

Verdict: WRONG ANSWER

Test 6

Group: 2

Verdict: WRONG ANSWER

Test 7

Group: 2

Verdict: WRONG ANSWER

Test 8

Group: 2

Verdict: WRONG ANSWER

Test 9

Group: 2

Verdict: WRONG ANSWER

Test 10

Group: 2

Verdict: WRONG ANSWER

Test 11

Group: 3

Verdict: WRONG ANSWER

Test 12

Group: 3

Verdict: WRONG ANSWER

Test 13

Group: 3

Verdict: WRONG ANSWER

Test 14

Group: 3

Verdict: WRONG ANSWER

Test 15

Group: 3

Verdict: WRONG ANSWER