Tunnels

input/code.cpp: In function 'int main()':
input/code.cpp:13:23: 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:16:33: 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 <stdio.h>

int N,M,I[100010],O[100010],P[100010],C[100010],E[100010];

int find(int x)
{
	if (P[x] != x) P[x] = find(P[x]);
	return P[x];
}

int main()
{
	scanf ("%d %d",&N,&M);
	for (int i=1;i<=N;i++) P[i] = i;
	for (int i=1;i<=M;i++){
		int x,y; scanf ("%d %d",&x,&y);
		I[x]++; O[y]++;
		P[find(x)] = find(y);
	}

	for (int i=1;i<=N;i++) if (I[i] > O[i]){
		C[find(i)] += I[i] - O[i];
		E[find(i)] += I[i];
	}
	
	int ans = 0;
	for (int i=1;i<=N;i++) if (i == find(i)){
		if (E[i]){
			if (C[i] == 0) ans++;
			else ans += C[i];
		}
	}

	printf ("%d\n",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