BC:so easy

Posted 2020-06-29

so easy

Accepts: 512

Submissions: 1601

Time Limit: 2000/1000 MS (Java/Others)

Memory Limit: 65536/65536 K (Java/Others)

Problem Description

Given an array with n integers, assume f(S) as the result of executing xor operation among all the elements of set S. e.g. if S={1,2,3} then f(S)=0.

your task is: calculate xor of all f(s), here s⊆S.

Input

This problem has multi test cases. First line contains a single integer T(T≤20) which represents the number of test cases. For each test case, the first line contains a

single integer number n(1≤n≤1,000) that represents the size of the given set. then the following line consists of nnn different integer numbers indicate elements

≤10?9??) of the given set.

Output

For each test case, print a single integer as the answer.

1
3
1  2  3

Sample Output

0

In the sample，S={1,2,3}, subsets of SSS are: ∅，{1}, {2}, {3}, {1, 2}, {1, 3}, {2, 3}, {1, 2, 3}


水题一只。当n>2时，无论给出的S是什么，最后的结果都是0。首先，X^X=0;一个集合的子集有2^n-1个，一个元素能n-1一个元素进行2^(n-1)-1次组
合，在加自己本身单独
一个子集，所以，任何元素在所有子集中出现的次数一定是偶数次，所以异或之后一定为0。

#include<cstdio>
#include<iostream>
using namespace std;
int main()
{
    int T;
    cin>>T;
    while(T--)
    {
        int n;
        cin>>n;
        int a[1005];
        for(int i=1;i<=n;i++)
            scanf("%d",&a[i]);
            if(n==1)
                cout<<a[1]<<endl;
            else
                cout<<"0"<<endl;

    }

}