Submission #1868385

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Source Code Expand

#include <algorithm>
#include <iostream>
#include <cstring>
#include <cstdio>
#include <cmath>
using namespace std;

inline int getint()
{
	static char c;
	while ((c = getchar()) < '0' || c > '9');

	int res = c - '0';
	while ((c = getchar()) >= '0' && c <= '9')
		res = res * 10 + c - '0';
	return res;
}

const int MaxN = 100000;
const int MaxM = 200;
const int MaxNV = MaxM * 2;

int n, m;
int in[MaxNV + 1], out[MaxNV + 1];

int ufs[MaxNV + 1];

int ufs_find(int v)
{
	return ufs[v] == v ? v : ufs[v] = ufs_find(ufs[v]);
}

int main()
{
	cin >> n >> m;

	for (int u = 1; u <= m + m; ++u)
		ufs[u] = u;

	for (int i = 0; i < n; ++i)
	{
		int a = getint(), b = getint();
		int c = getint(), d = getint();

		int u = c ? c + m : a;
		int v = d ? d : m + b;

		++out[u], ++in[v];

		ufs[ufs_find(v)] = ufs_find(u);
	}

	bool ok = true;

	for (int u = 1; u <= m; ++u)
		if (out[u] < in[u])
			ok = false;

	for (int v = 1; v <= m; ++v)
		if (out[v + m] > in[v + m])
			ok = false;

	for (int u = 1; u <= m + m; ++u)
		if (ufs[u] == u && (in[u] || out[u]))
		{
			bool all = true;
			for (int v = 1; v <= m + m; ++v)
				if (ufs_find(v) == u)
					all &= in[v] == out[v];

			if (all)
				ok = false;
		}

	puts(ok ? "YES" : "NO");

	return 0;
}

Submission Info

Judge Result