Chessboard(二分图完备匹配)

wa找不到原因，却是In the next k lines, there is a pair of integers (x, y) in each line, which represents a hole in the y-th row, the x-th column。

关键在于建立图的过程，本题是典型的黑白染色法建立图形，

#include <iostream>
#include <cstring>
#include <cstdio>
using namespace std;
const int MAXN = 35*35;
int vN, uN;
bool g[MAXN][MAXN];
bool clr[MAXN][MAXN];
int xM[MAXN], yM[MAXN];
bool chk[MAXN];
int dx[] = {-1,0, 1, 0};
int dy[] = {0, 1, 0, -1};

bool searchPath(int u)
{
	int v;
	for(v = 0; v < vN; v++)
		if(g[u][v] && !chk[v])
		{
			chk[v] = true;
			if(yM[v] == -1 || searchPath(yM[v])) 
			{
				yM[v] = u;
				xM[u] = v;
				return true;
			}
		}
		return false;
}

int maxMatch()
{
	int u, ret = 0;
	memset(xM, -1, sizeof(xM));
	memset(yM, -1, sizeof(yM));
	for(u = 0; u < uN; u++)
		if(xM[u] == -1)
		{
			memset(chk,  false, sizeof(chk));
			if(searchPath(u))ret++;
		}
		return ret;
}
bool check(int x, int y, int m, int n)
{
	return x>=0 && x < m && y>=0 && y<n;
}
int main()
{
	int m,n,k,a,b;
	clr[0][0] = 1;
	int i,j;
	//给每一个部分染色 
	for(i =1; i < MAXN; i++)clr[0][i] = !clr[0][i-1];
	for(i = 1; i < MAXN; i++)
		for(j = 0; j < MAXN; j++)
			clr[i][j]= !clr[i-1][j];
	//end 染色	
		memset(g, 0, sizeof(g));
		scanf("%d%d%d",&m, &n, &k);
		int num[35][35];
		memset(num, 0, sizeof(num));
		
		//标记坏点，将a,b转换为数组下标 
		while(k--)
		{
			scanf("%d%d", &a, &b);
			a--;
			b--;
			num[b][a] = -1;
		}
		
		//统计出二分图矩阵的大小uN*vN 
		int cnt = 0;
		uN = vN = 0;
		for(i = 0; i < m; i++)
			for(j = 0; j < n; j++)
			{
				if(num[i][j] != -1)
				{
					if(clr[i][j]){num[i][j] = uN++;}
					else {num[i][j] = vN++;}
				}
			}
			
			
			if(uN != vN)
			{
				puts("NO");
			}
			else 
			{//建二分图，找相互连接的边 
				int ni,nj;
				for(i = 0; i < m; i++)
					for(j = 0; j < n; j++)
						if(num[i][j]!=-1 && clr[i][j])
						{
							for(k = 0; k < 4; k++)
							{
								ni = i + dx[k];
								nj = j + dy[k];
								if(check(ni,nj, m,n) && num[ni][nj]!=-1 )
								{
									g[num[i][j]][num[ni][nj]] = 1;
								}
							}
						}
						
				//如果可以完备匹配则成功，否则不成功		
				if(maxMatch() == vN)puts("YES");
				else puts("NO");
			}
			
	system("pause");
	return 0;
}