Submission #826154

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Source Code Expand

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

#define pb         push_back

typedef long long ll;
const ll INF = 1000000000ll;
const ll MOD = 1000000007ll;
const double EPS = 1e-8;

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


	int n, m;
	cin >> n >> m;
	vector<int> box(n, 1);
	box[0] = 0;
	vector<int> rbox(n, 0);
	rbox[0] = 1;
	vector<int> x;
	vector<int> y;
	vector<int> nx(n, 0);
	vector<int> ny(n, 0);
	vector<bool> flag(n, false);

	for(int i=0; i<m; i++){
		int t1, t2;
		cin >> t1 >> t2;
		t1--; t2--;
		x.push_back(t1);
		y.push_back(t2);
		nx[t1]++;
		ny[t2]++;
	}
	if(ny[0] + box[0] - nx[0] >= 0){
		flag[0] == true;
	}
	for(int i=0; i<m; i++){
		int tx = x[i];
		int ty = y[i];
		nx[tx]--;
		ny[ty]--;
		if(rbox[tx] == 1){
			if(ny[ty] + box[ty] - nx[ty] >= 0){
				//printf("%d %d %d\n", i, tx, ty);
				flag[ty] = true;
			}
			rbox[tx] = 0;
			rbox[ty] = 1;
		}else{
			box[tx]--;
			box[ty]++;
		}
	}

	int ans = 0;
	for(int i=0; i<n; i++){
		//cout << flag[i] << endl;
		if(flag[i]) ans++;
	}

	cout << ans << endl;

	return 0;
}

Submission Info

Judge Result