poj 2362 Square

#include<iostream>
#include<algorithm>
using namespace std;
#define MAX 21
int n;
int len;
int parts;
int max;
int sum;
int a[MAX];
bool used[MAX];
bool pt(int a,int b)
{
return a>b;
}
//cnt: 当前长度
//tot: 找到几段木棒了
//I：为数组下标
bool dfs(int cnt, int tot, int I)
{
int i;
if(tot == parts)
return true;
for(i=I; i<n; i++)
{
if(i && !used[i-1] && a[i-1] == a[i])
continue;
if(!used[i])
{
if(cnt + a[i] < len)
{
used[i] = true;
if(dfs(cnt+a[i], tot, i+1))
return true;
used[i] = false;
}
else if(cnt + a[i] == len)
{
used[i] = true;
if(dfs(0, tot+1, 0))
return true;
used[i] = false;
}
if(cnt == 0)
break;
}
}
return false;
}
int main()
{
//freopen("in.txt", "r", stdin);
int i, t;
scanf("%d", &t);
while(t--)
{
scanf("%d", &n);
sum = 0;
for(i=0; i<n; i++)
{
scanf("%d", &a[i]);
sum += a[i];
used[i] = false;
}
sort(a, a+n, pt);
len = sum / 4;
parts = 4;
if(sum % 4 == 0 && dfs(0, 1, 0))
printf("yes/n");
else
printf("no/n");
}
return 0;
}