Brexit

#include <iostream>
#include <vector>

const int N = 2 * (1e5) + 5;
const int inf = 1e9;
std::vector<int> conns [N];
int rem [N];

int main() {
	std::ios_base::sync_with_stdio(false);
	std::cin.tie(0);

	int n, m, x, l;
	std::cin >> n >> m >> x >> l;
	--x; --l;

	for (int i = 0; i < m; ++i) {
		int a, b;
		std::cin >> a >> b;
		--a; --b;
		conns[a].push_back(b);
		conns[b].push_back(a);
	}
	for (int i = 0; i < n; ++i) {
		rem[i] = (int)conns[i].size();
	}
	bool res = false;
	rem[l] = inf;
	std::vector<int> remove;
	remove.push_back(l);
	for (int j = 0; j < (int)remove.size(); ++j) {
		int i = remove[j];
		if (i == x) res = true;
		for (int s = 0; s < (int)conns[i].size(); ++s) {
			int t = conns[i][s];
			--rem[t];
			if (rem[t] <= (int)conns[t].size() / 2) {
				remove.push_back(t);
				rem[t] = inf;
			}
		}
	}
	std::cout << (res ? "leave" : "stay") << '\n';
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED

Test 18

Verdict: ACCEPTED

Test 19

Verdict: ACCEPTED

Test 20

Verdict: ACCEPTED

Test 21

Verdict: ACCEPTED

Test 22

Verdict: ACCEPTED

Test 23

Verdict: ACCEPTED

Test 24

Verdict: ACCEPTED

Test 25

Verdict: ACCEPTED

Test 26

Verdict: ACCEPTED

Test 27

Verdict: ACCEPTED

Test 28

Verdict: ACCEPTED

Test 29

Verdict: ACCEPTED

Test 30

Verdict: ACCEPTED

Test 31

Verdict: ACCEPTED

Test 32

Verdict: ACCEPTED

Test 33

Verdict: ACCEPTED

Test 34

Verdict: ACCEPTED

Test 35

Verdict: ACCEPTED