poj 2446

简单二分图匹配

#include<stdio.h>
#include<string.h>
#define con 1100
int m,n,p;           //m=row,n=col
int map[con][con];
int cx[con],cy[con];
bool mk[con];
bool is[33][33];
int path(int u){
	int i;
	for(i=0;i<m*n;i++){
		if(map[u][i] && mk[i]==0){
			mk[i]=1;
			if(cy[i]==0 || path(cy[i])){
				cx[u]=i;
				cy[i]=u;
				return 1;
			}
		}
	}
	return 0;
}

int maxmatch(){
	int i,j,u,v,sum=0;
	memset(cx,0,sizeof(cx));
	memset(cy,0,sizeof(cy));
	for(i=0;i<m*n;i++){
		if(cx[i]==0){
			memset(mk,0,sizeof(mk));
			sum+=path(i);
		}
	}
	return sum;
}
bool isok(int u,int v){
	if(u>=0 && v>=0 && u<m && v<n && !is[u][v])
		return 1;
	return 0;
}
int main(){
	int i,j,u,v,t=1;
	scanf("%d %d %d",&m,&n,&p);
	memset(map,0,sizeof(map));
	memset(is,0,sizeof(is));
	for(i=1;i<=p;i++){
		scanf("%d %d",&u,&v);       //u is col,v is row
		is[v-1][u-1]=1;
	}
	for(i=0;i<m;i++)
		for(j=0;j<n;j++){
			if(is[i][j])
				continue;
			if(isok(i+1,j))
				map[i*n+j][(i+1)*n+j]=1;
			if(isok(i,j+1))
				map[i*n+j][i*n+j+1]=1;
			if(isok(i,j-1))
				map[i*n+j][i*n+j-1]=1;
			if(isok(i-1,j))
				map[i*n+j][(i-1)*n+j]=1;
		}
	if(maxmatch()==(m*n-p))
		printf("YES\n");
	else
		printf("NO\n");
}