Tunnelit

input/code.cpp: In function 'int main()':
input/code.cpp:44:11: warning: 'c' may be used uninitialized in this function [-Wmaybe-uninitialized]
  while(r[c].size() > 0) c = r[c][0];
           ^

#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

vector<vector<int>> v, r;
vector<bool> z;
int s = 1;

void f(int x) {
	bool y = true;
	
	for(auto i : v[x]) {
		if(z[i]) continue;
		else z[i] = true;
		
		f(i);
		
		if(y) y = false;
		else s++;
	}
}

int main() {
	cin.tie(0);
	ios_base::sync_with_stdio(false);
	
	int n, m, a, b;
	cin >> n >> m;	
	
	v.resize(n);
	r.resize(n);
	z.resize(n);
	
	for(int i = 0; i < m; i++) {
		cin >> a >> b;
		v[a-1].push_back(b-1);
		r[b-1].push_back(a-1);
	}
	
	int c;
	for(int i = 0; i < n; i++) if(v[i].size() > 0) c = i;
	
	while(r[c].size() > 0) c = r[c][0];
	
	f(c);
		
	cout << s << endl;
}

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