Tunnels

input/code.cpp: In function 'int main()':
input/code.cpp:29:22: 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:34:48: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d %d",&data[i].first,&data[i].second);
                                                ^

#include <bits/stdc++.h>
#define MAXN 200005
#define MYINF 1000000000

using namespace std;

static int s[MAXN];
static int a[MAXN];
int res;
static char b[MAXN];
static int o[MAXN];
int oc;
static int e[MAXN];

void DFS (int point) {
	if (b[point]) {
		return;
	}
	b[point] = 1;
	for (int i = s[point]; i < s[point+1]; i++) {
		DFS(a[i]);
	}
	o[oc] = point;
	oc++;
}

int main () {
	int N, M;
	scanf("%d %d",&N,&M);
	static pair<int, int> data[MAXN];
	memset(s, 0, sizeof(s));
	int i;
	for (i = 0; i < M; i++) {
		scanf("%d %d",&data[i].first,&data[i].second);
		data[i].first--;
		data[i].second--;
		s[data[i].first]++;
	}
	for (i = 1; i <= N; i++) {
		s[i] += s[i-1];
	}
	for (i = 0; i < M; i++) {
		s[data[i].first]--;
		a[s[data[i].first]] = data[i].second;
	}
	oc = 0;
	memset(b, 0, sizeof(b));
	for (i = 0; i < N; i++) {
		DFS(i);
	}
	res = 0;
	memset(e, 0, sizeof(e));
	for (i = oc-1; i >= 0; i--) {
		int point = o[i];
		res += max(0, (s[point+1] - s[point]) - e[point]);
		for (int j = s[point]; j < s[point+1]; j++) {
			e[a[j]]++;
		}
	}
	printf("%d\n", res);
	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