Fire Net HDU 1045

简单深搜，可以完全暴力，不会超时的。

#include<iostream>

#include<cstring>

#include<cmath>

using namespace std;

#define MAX(a,b) (a>b?a:b) 

char maze[10][10];

int n, maxn;



void DFS(int step,int count);

int cheak(int x, int y);

int main()

{

    int i;

    while(scanf("%d",&n), n)

    {

        maxn = 0;

        for(i = 0; i < n; i++)

            scanf("%s",maze[i]);

        DFS(0,0);

        printf("%d\n",maxn);

    }

    return 0;

}



void DFS(int step,int count)

{

    int x, y;

    maxn = MAX(maxn,count);

    if(step == n*n)

        return ;

    x = step/n;

    y = step%n;

    if(maze[x][y] == '.' && cheak(x,y))

    {

        maze[x][y] = 'O';

        DFS(step+1,count+1);

        maze[x][y] = '.';

    }

    DFS(step + 1, count);

}



int cheak(int x, int y)

{

    int i;

    for(i = x-1; i >= 0; i--)

    {

        if(maze[i][y] == 'O')

            return 0;

        else if(maze[i][y] == 'X')

            break;

    }

    for(i = y-1; i >= 0; i--)

    {

        if(maze[x][i] == 'O')

            return 0;

        else if(maze[x][i] == 'X')

            break;

    }

    return 1;

}