Trouble&&http://acm.hdu.edu.cn/showproblem.php?pid=4334

[align=left]Problem Description[/align]
Hassan is in trouble. His mathematics teacher has given him a very difficult problem called 5-sum. Please help him.

The 5-sum problem is defined as follows: Given 5 sets S_1,...,S_5 of n integer numbers each, is there a_1 in S_1,...,a_5 in S_5 such that a_1+...+a_5=0?

[align=left]Input[/align]
First line of input contains a single integer N (1≤N≤50). N test-cases follow. First line of each test-case contains a single integer n (1<=n<=200). 5 lines follow each containing n integer numbers in range [-10^15, 1 0^15]. I-th
line denotes set S_i for 1<=i<=5.

[align=left]Output[/align]
For each test-case output "Yes" (without quotes) if there are a_1 in S_1,...,a_5 in S_5 such that a_1+...+a_5=0, otherwise output "No".

[align=left]Sample Input[/align]

2
2
1 -1
1 -1
1 -1
1 -1
1 -1
3
1 2 3
-1 -2 -3
4 5 6
-1 3 2
-4 -10 -1

[align=left]Sample Output[/align]

No
Yes题意：给你5行数，问你是不是存在这一组数，在每行取一个，使得所求的和为0，思路：如果直接暴力，五成for循环肯定会挂掉，，这里可以用hash表优化成三层for循环，，AC代码：

#include<iostream>
#include<string.h>
#include<string>
#define N 100005
using namespace std;
__int64 aa[5][205];
__int64 Hash
;
bool flag
;
int _Hash(__int64 num)
{
int t=num%N;
if(t<0) t+=N;
while(flag[t]&&Hash[t]!=num)  t=(t+1)%N;
return t;
}
int main()
{
int T;
scanf("%d",&T);
while(T--)
{
memset(flag,false,sizeof(flag));
int n;
scanf("%d",&n);
for(int i=0;i<5;i++){
for(int j=0;j<n;j++)
scanf("%I64d",&aa[i][j]);
}
memset(flag,0,sizeof(flag));
for(int i=0;i<n;i++)
for(int j=0;j<n;j++){
__int64 num=-(aa[0][i]+aa[1][j]);
int pos=_Hash(num);
Hash[pos]=num;
flag[pos]=true;
}
bool fflag=false;
for(int i=0;i<n;++i)
for(int j=0;j<n;++j)
for(int k=0;k<n;++k)
{
__int64 num=(aa[2][i]+aa[3][j]+aa[4][k]);
int pos=_Hash(num);
if(flag[pos]) {fflag=true;i=j=n;break;}
}
if(fflag) printf("Yes\n");
else printf("No\n");
}return 0;
}