Tunnels

input/code.cpp: In function 'int main()':
input/code.cpp:26:26: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d", &n, &m);
                          ^
input/code.cpp:28:40: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         int u, v; scanf("%d%d", &u, &v);
                                        ^

#include <bits/stdc++.h>
using namespace std;

typedef long long LL;
typedef pair<int, int> II;

const int N = (int) 1e5 + 10;
int n, m, deg[N], sum;
vector<int> adj[N];
bool fre[N];

void DFS(int u) {
    fre[u] = false; if (deg[u] > 0) sum += deg[u];
    for (int i = 0; i < (int) adj[u].size(); ++i) {
        int v = adj[u][i];
        if (fre[v]) DFS(v);
    }
}

int main() {
    #ifdef LOCAL
        freopen("Data.inp", "r", stdin);
        freopen("Data.out", "w", stdout);
    #endif

    scanf("%d%d", &n, &m);
    while (m--) {
        int u, v; scanf("%d%d", &u, &v);
        deg[u]--; deg[v]++;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }

    int ans = 0; memset(fre, true, sizeof fre);
    for (int i = 1; i <= n; ++i) if (fre[i]) {
        sum = 0; DFS(i);
        ans += sum;
    }

    printf("%d", ans);
    return 0;
}

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