Coprime Sequence

Problem Description

Do you know what is called ``Coprime Sequence''? That is a sequence consists of n positive integers, and the GCD (Greatest Common Divisor) of them is equal to 1.
``Coprime Sequence'' is easy to find because of its restriction. But we can try to maximize the GCD of these integers by removing exactly one integer. Now given a sequence, please maximize the GCD of its elements.

 

Input

The first line of the input contains an integer T(1≤T≤10), denoting the number of test cases.
In each test case, there is an integer n(3≤n≤100000) in the first line, denoting the number of integers in the sequence.
Then the following line consists of n integers a1,a2,...,an(1≤ai≤109), denoting the elements in the sequence.

 

Output

For each test case, print a single line containing a single integer, denoting the maximum GCD.

 

Sample Input

3
3
1 1 1
5
2 2 2 3 2
4
1 2 4 8

 

Sample Output

1
2
2

题意：去掉一个数字，求最大的gcd；

#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
int a[100009];
int main()
{
    int T;
    scanf("%d",&T);
    while(T--)
    {
        int n;
        scanf("%d",&n);
        for(int i=0;i<n;i++)
            scanf("%d",&a[i]);
        int flag=0,k=a[0],x,p=a[0];
        a[0]=0;
        for(int i=1;i<n;i++)
        {
            x=__gcd(k,a[i]);
            if(x<k)
            {
                a[flag]=p;
                p=a[i];
                flag=i;
                a[i]=0;
                k=x;
            }
        }
        int q=0;
        for(int i=0;i<n;i++)
        {
            if(a[i]&&!q)
            {
                q=1;
                k=a[i];
            }
            else
            {
                k=__gcd(k,a[i]);
            }
        }
        printf("%d\n",k);
    }
    return 0;
}