HDU 5536 Chip Factory（暴力+优化）

John is a manager of a CPU chip factory, the factory produces lots of chips everyday. To manage large amounts of products, every processor has a serial number. More specifically, the factory produces nn chips today, the ii-th chip produced this day has a serial number sisi. 

At the end of the day, he packages all the chips produced this day, and send it to wholesalers. More specially, he writes a checksum number on the package, this checksum is defined as below: 

maxi,j,k(si+sj)⊕skmaxi,j,k(si+sj)⊕sk

which i,j,ki,j,k are three different integers between 11 and nn. And ⊕⊕ is symbol of bitwise XOR. 

Can you help John calculate the checksum number of today?

Input

The first line of input contains an integer TT indicating the total number of test cases. 

The first line of each test case is an integer nn, indicating the number of chips produced today. The next line has nn integers s1,s2,..,sns1,s2,..,sn, separated with single space, indicating serial number of each chip. 

1≤T≤10001≤T≤1000 
3≤n≤10003≤n≤1000 
0≤si≤1090≤si≤109 
There are at most 1010 testcases with n>100n>100

Output

For each test case, please output an integer indicating the checksum number in a line.

Sample Input

231 2 33100 200 300

Sample Output

6400

题解：

题意：

给你一个序列，找出三个不同的i，j，k，使得(a[i]+a[j])^a[k]最大

思路： 

暴力+一些剪枝可以过

代码：

#include<iostream>#include<cstring>#include<stdio.h>#include<math.h>#include<string>#include<stdio.h>#include<queue>#include<stack>#include<map>#include<vector>#include<deque>#include<algorithm>#define ll long long#define INF 100861111#define M (t[k].l+t[k].r)/2#define lson k*2#define rson k*2+1using namespace std;int a[1005];int main(){    int i,j,k,d,test,maxx,n;    scanf("%d",&test);    while(test--)    {        scanf("%d",&n);        maxx=0;        for(i=0;i<n;i++)            scanf("%d",&a[i]);        for(i=0;i<n;i++)        {            for(j=i+1;j<n;j++)            {                for(k=j+1;k<n;k++)                {                    maxx=max(maxx,(a[i]+a[j])^a[k]);                    maxx=max(maxx,(a[j]+a[k])^a[i]);                    maxx=max(maxx,(a[i]+a[k])^a[j]);                }            }        }        printf("%d\n",maxx);    }}