Tunnels

input/code.cpp: In function 'int main()':
input/code.cpp:16:44: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     int n, m, rez = 0; scanf("%d%d", &n,&m);
                                            ^
input/code.cpp:18:44: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
             int x, y; scanf("%d%d", &x, &y);
                                            ^

#include <bits/stdc++.h>
#define MAXN 100010
using namespace std;
stack<int> degnula;
int degin[MAXN], degins;
stack<int> a[MAXN];
void dfs(int node) {
    degin[node]--;
    if(degin[node] == 0) degnula.push(node),degins++;
    if(!a[node].empty()) {
            dfs(a[node].top());
            a[node].pop();
    }
}
int main() {
    int n, m, rez = 0; scanf("%d%d", &n,&m);
    for(int i = 0; i < m; i++) {
            int x, y; scanf("%d%d", &x, &y);
            a[x].push(y);
            degin[y]++;
    }
    for(int i = 1; i <= n; i++) {
        if(degin[i] == 0) degnula.push(i), degins++;
    }
    while(!degnula.empty()) {
        int cur = degnula.top(); degnula.pop();
        while(!a[cur].empty())
            dfs(cur), rez++;
    }
    printf("%d", rez);
}

Test 1

Group: 1

Verdict: ACCEPTED

Test 2

Group: 1

Verdict: ACCEPTED

Test 3

Group: 1

Verdict: ACCEPTED

Test 4

Group: 1

Verdict: ACCEPTED

Test 5

Group: 1

Verdict: ACCEPTED

Test 6

Group: 2

Verdict: ACCEPTED

Test 7

Group: 2

Verdict: ACCEPTED

Test 8

Group: 2

Verdict: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED

Test 11

Group: 3

Verdict: ACCEPTED

Test 12

Group: 3

Verdict: ACCEPTED

Test 13

Group: 3

Verdict: ACCEPTED

Test 14

Group: 3

Verdict: ACCEPTED

Test 15

Group: 3

Verdict: ACCEPTED