hdu 1045 DFS回溯

#include <iostream>using namespace std;int n;char map[5][5];int res;bool judge(int x,int y){for(int i = x; i >= 0; i--){if(map[i][y] == '0'){return false;}if(map[i][y] == 'X'){break;}}for(int j = y; j >= 0; j--){if(map[x][j] == '0'){return false;}if(map[x][j] == 'X'){break;}}return true;}void DFS(int i,int a){if(i == n*n){if(a > res){res = a;}return;}int x,y;x = i/n;y = i%n;if(map[x][y] == '.' && judge(x,y) == true){map[x][y] = '0';DFS(i+1,a+1);map[x][y] = '.';}DFS(i+1,a);}int main(){while(cin>>n){if(n == 0){break;}for(int i = 0; i < n; i++){for(int j = 0; j < n; j++){cin>>map[i][j];}}res = 0;int num = 0;DFS(num,0);cout<<res<<endl;}return 0;}