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题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=1518
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3 4 1 1 1 1 5 10 20 30 40 50 8 1 7 2 6 4 4 3 5
yes no yes
题意：
问所给的短棒能否组成一个正方形。
代码如下：
#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
int a[32], vis[32];
int flag, sum, tsum, n;
void dfs(int edge,int len,int pos)
{
int i;
if(edge == 4)
{
flag = 1;
return ;
}
if(len == tsum)
{
dfs(edge+1,0,0);//从0开始重新搜索
if(flag)
return ;
}
for(i = pos; i < n; i++)
{
if(!vis[i] && len+a[i] <= tsum)
{
vis[i] = 1;
dfs(edge,a[i]+len,i+1);
if(flag)
return;
vis[i] = 0;
}
}
}
int main()
{
int t, i;
while(~scanf("%d",&t))
{
while(t--)
{
memset(vis,0,sizeof(vis));
sum = 0, flag = 0;
scanf("%d",&n);
for(i = 0; i < n; i++)
{
scanf("%d",&a[i]);
sum+=a[i];
}
if(sum%4 != 0)
{
printf("no\n");
continue;
}
tsum = sum/4;
for(i = 0; i < n; i++)
{
if(a[i] > tsum)
{
flag = 1;
break;
}
}
if(flag == 1)
{
printf("no\n");
continue;
}
dfs(0,0,0);
if(flag)
printf("yes\n");
else
printf("no\n");
}
}
return 0;
}
hdu 1518 Square（深搜dfs）,布布扣,bubuko.com
原文地址：http://blog.csdn.net/u012860063/article/details/37901013
