zoj 1002解题报告

第一道dfs,值得纪念

#include <stdio.h>
const int max=5;
char map[max][max];
int visit[max][max];
int count,k,maxn,n;
int judge(int x,int y)
{
	int i,j;
	for(i=x,j=y-1;j>=0;j--)
	{
		if(visit[i][j]==1) return 0;
		else if(map[i][j]=='X') break;
	}
	for(j=y,i=x-1;i>=0;i--)
	{
		if(visit[i][j]==1) return 0;
		else if(map[i][j]=='X') break;
	}
	return 1;
}
void dfs(int k,int count)
{
	int xn,yn;
	if(k==n*n)
	{
		if(count>maxn)
		{
			maxn=count;
		}
		return;

	}
	else
	{
		xn=k/n;
		yn=k%n;
		if(visit[xn][yn]==0&&judge(xn,yn)&&map[xn][yn]=='.')
		{
			count++;
			visit[xn][yn]=1;
			dfs(k+1,count);
			visit[xn][yn]=0;
			count--;

		}

		dfs(k+1,count);
	}
	
}


int main()
{
	int i,j;
	while(scanf("%d",&n)==1)
	{
		if(n==0) break;
		count=0;
		k=0;
		maxn=0;
		for(i=0;i<n;i++)
		{
			getchar();
			for(j=0;j<n;j++)
			{
				scanf("%c",&map[i][j]);
				visit[i][j]=0;
			}
		}
		dfs(0,0);
		printf("%d\n",maxn);
	}

	return 0;
}