poj 1321 棋盘问题 简单dfs

这么简单一道题目，想了这么久，还wa了一次，不可饶恕啊，越来越觉得自己笨了，dfs搜索都快不会写了。。。逻

辑混乱，一定得认真想题目，认真写代码：

代码：

#include<iostream>#include<cstdio>#include<cstdlib>#include<cstring>#include<cmath>#include<vector>#include<set>#include<string>#include<algorithm>#define MAX 0x7fffffffusing namespace std;int sum,cnt,m,ans;struct node{int i,j;}gra[70];int visit[2][70];void dfs(int num,int ans){if(ans == m){cnt++;return ;}for(int i=num+1; i<=sum; i++){if(!visit[0][gra[i].i] && !visit[1][gra[i].j]){visit[0][gra[i].i] = 1;visit[1][gra[i].j] = 1;ans ++;dfs(i,ans);ans --;visit[1][gra[i].j] = 0;visit[0][gra[i].i] = 0;}}return ;}int main(){int n,k,i,j;char ch;while(cin >> n >> m) {if(n == -1 && m == -1)break;memset(visit,0,sizeof(visit));cnt = 0;getchar();int k = 1;for(i=1; i<=n; i++){for(j=1; j<=n; j++){cin >> ch;if(ch == '#'){gra[k].i = i;gra[k].j = j;k++;}}getchar();}sum = k-1;dfs(0,0);cout << cnt << endl;}return 0;}