uva639 回溯

标签：uva639   dfs   回溯   

//
//  main.cpp
//  639
//
//  Created by Fangpin on 15/3/9.
//  Copyright (c) 2015年 FangPin. All rights reserved.
//

#include <iostream>
#include <cstring>
#include <cstdio>
#include <string>
using namespace std;
int map[7][7];
int ans,n;
void dfs(int x,int y,int sum){
    if(!map[x][y]){
        ++y;
        if(y==n+1) {y=1;++x;}
        if(x<=n)
            dfs(x,y,sum);
    }
    else{
        int c1=0,c2=0,i=x,j=y;
        while(map[i][j]){
            if(map[i][j]==2) ++c1;
            ++i;
        }
        i=x;j=y;
        while(map[i][j]){
            if(map[i][j]==2) ++c1;
            --i;
        }
        i=x;j=y;
        while(map[i][j]){
            if(map[i][j]==2) ++c2;
            ++j;
        }
        i=x;j=y;
        while(map[i][j]){
            if(map[i][j]==2) ++c2;
            --j;
        }
        if(c1 || c2){
            ++y;
            if(y==n+1) {y=1;++x;}
            if(x<=n)
                dfs(x,y,sum);
        }
        else{
            ++sum;
            ans=max(ans,sum);
            int i=x,j=y;
            ++y;
            if(y==n+1) {y=1;++x;}
            if(x<=n){
                map[i][j]=2;
                dfs(x,y,sum);
                --sum;
                map[i][j]=1;
                dfs(x,y,sum);
            }
        }
    }
}

int main(int argc, const char * argv[]) {
    // insert code here...
    while(scanf("%d",&n),n){
        memset(map,0,sizeof(map));
        string s;
        for(int i=1;i<=n;++i){
            cin>>s;
            for(int j=0;j<s.size();++j){
                if(s[j]=='.')
                    map[i][j+1]=1;
                else map[i][j+1]=0;
            }
        }
        ans=0;
        dfs(1,1,0);
        printf("%d\n",ans);
    }
    return 0;
}

uva639 回溯

标签：uva639   dfs   回溯   

原文地址：http://blog.csdn.net/fangpinlei/article/details/44156815