Coprime Sequence HDU

Do you know what is called ``Coprime Sequence''? That is a sequence consists of nn 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)T(1≤T≤10), denoting the number of test cases.
In each test case, there is an integer n(3≤n≤100000)n(3≤n≤100000) in the first line, denoting the number of integers in the sequence.
Then the following line consists of nn integers a1,a2,...,an(1≤ai≤109)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

#include<stdio.h>#include<algorithm>using namespace std;#define N 100001int gcd(int a,int b){    if(!b)        return a;    return gcd(b,a%b);}int main(){    int t,res[N],left[N],right[N];    scanf("%d",&t);    while(t--)    {        int n;        scanf("%d",&n);        for(int i=1; i<=n; i++)            scanf("%d",&res[i]);        left[1]=res[1];        right[n]=res[n];        for(int i=2; i<=n; i++)            left[i]=gcd(left[i-1],res[i]);        for(int i=n-1; i>=1; i--)            right[i]=gcd(right[i+1],res[i]);        int s=max(left[n-1],right[2]);        //left[n-1]表示去掉最后一个的最大公约数        //right[2]表示去掉第一个的最大公约数        for(int i=2; i<=n-1; i++)            s=max(s,gcd(left[i-1],right[i+1]));        printf("%d\n",s);    }    return 0;}