POJ 3740 Easy Finding(dfs回溯)

3 3
0 1 0
0 0 1
1 0 0
4 4
0 0 0 1
1 0 0 0
1 1 0 1
0 1 0 0

Yes, I found it
It is impossible

这是一道子集枚举的回溯题，针对当前行选不选进行回溯，并且进行剪枝。

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
#define maxn 1005
int n,m;
int a[20][305];
int vis[305];
bool judge(){
   for(int i=0;i<n;i++)
    if(vis[i]==0)return false;
   return true;
}
bool judges(){
   for(int i=0;i<n;i++)
    if(vis[i]>1)return false;
   return true;
}
bool dfs(int cur)
{
    if(judge())return true;
    if(cur>=m)return judge();
    for(int i=0;i<n;i++){
        if(a[cur][i]==1)vis[i]++;
    }
    if(judges()){
        if(dfs(cur+1))return true;
    }
    for(int i=0;i<n;i++){
        if(a[cur][i]==1)vis[i]--;
    }
    if(dfs(cur+1))return true;
    return false;
}
int main()
{
    //freopen("in.txt","r",stdin);
    while(scanf("%d%d",&m,&n)!=EOF){
        for(int i=0;i<m;i++)
            for(int j=0;j<n;j++)
            scanf("%d",&a[i][j]);
        memset(vis,0,sizeof vis);
        if(dfs(0))puts("Yes, I found it");
        else puts("It is impossible");

    }

}

POJ 3740 Easy Finding(dfs回溯)

原文：http://blog.csdn.net/u013497977/article/details/43229593