不知道哪里错了~~~~

#include<iostream>
#include<cstdio>
#include<cmath>
#include<cstring>
#include<algorithm>
using namespace std;
const int xmax = 600, ymax = 600;
int xN, yN;
bool g[xmax][ymax];
int xM[xmax],yM[ymax];
bool chky[ymax];
int Q[1300], prev[xmax];

int MaxMatch() {
	int res = 0;
	int qs, qe;
	memset(xM, -1, sizeof(xM));
	memset(yM, -1, sizeof(yM));
	memset(chky, -1, sizeof(chky));
	for (int i = 0; i < xN; i++){
		if (xM[i] == -1){
			qs = qe = 0;
			Q[qe++] = i;
			prev[i] = -1;
			bool flag = 0;
			while (qs < qe && !flag){
				int u = Q[qs];
				for (int v = 0; v < yN && !flag; v++){
					if (g[u][v] && chky[v] != i) {
						chky[v] = i; Q[qe++] = yM[v];
						if (yM[v] >= 0)
							prev[yM[v]] = u;
						else {
							flag = 1;
							int d = u, e = v;
							while (d != -1) {
								int t = xM[d];
								xM[d] = e; yM[e] = d;
								d = prev[d]; e = t;
							}
						}
					}
					qs++;
				}
			}
			if (xM[i] != -1) res++;
		}
	}
	return res;
}

bool map[40][40];
int idd[40][40];
int main(){
	int i, j, p, q;
	int n, m, k, x, y;
	while(~scanf("%d%d%d",&m,&n,&k)){
		memset(g,0,sizeof(g));
		if((m*n-k)&1){
			cout<<"NO"<<endl;
			continue;
		}
		memset(map,true,sizeof(map));
		for(i=0;i<k;i++){
			scanf("%d%d",&y,&x);
			map[x-1][y-1] = false;
		}
		p = q = 0;
		for(i=0;i<m;i++){
			for(j=0;j<n;j++){
				if(map[i][j]){
					if((i+j)&1)
						idd[i][j] = p++;
					else
						idd[i][j] = q++;
				}
			}
		}
		for(i=0;i<m;i++){
			for(j=0;j<n;j++){
				if(map[i][j]){
					if((i+j)&1){
						if(i-1>=0&&map[i-1][j])
							g[idd[i][j]][idd[i-1][j]] = 1;
						if(j-1>=0&&map[i][j-1])
							g[idd[i][j]][idd[i][j-1]] = 1;
						if(i+1<m&&map[i+1][j])
							g[idd[i][j]][idd[i+1][j]] = 1;
						if(j+1<n&&map[i][j+1])
							g[idd[i][j]][idd[i][j+1]] = 1;
					}
				}
			}
		}
		xN = p; yN=q;
		if(MaxMatch()==(m*n-k)/2){
			cout<<"YES"<<endl;
		}
		else
			cout<<"NO"<<endl;
	}
	return 0;
}