第六场选拔 Problem E: Subarray GCD 水

Problem E: Subarray GCD

Time Limit: 1 Sec  Memory Limit: 128 MB
Submit: 68  Solved: 34
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Description

Given an array A₁,A₂...A_N, you have to print the size of the largest contiguous subarray such that
GCD of all integers in that subarray is 1.

Formally,
For a subarray A_i,A_i+1...A_j where 1 ≤ i < j ≤ N to be valid: GCD(A_i,A_i+1...A_j) should be 1. You have to print the size of the largest valid subarray.

If no valid subarray exists, output -1.

Note:A single element is not considered as a subarray according to the definition of this problem.

Input

First line contains T, the number of testcases. Each testcase consists of N in one line followed by Nintegers in the next line.

Constraints

• 1 ≤ T ≤ 10
• 2 ≤ N ≤ 10⁵
• 1 ≤ A_i ≤ 10⁵

Output

For each testcase, print the required answer in one line.

Sample Input

2

2

7 2

3

2

2 4

Sample Output

2

-1







题意是求最大的一个序列，这个序列的所有数最大公约数为1，仔细想想，给定序列只要有一个子序列最大公约数为1，那么整个必定为1，如果不存在，那么这个序列的最大公约数不为1，所以把序列所有数取公约就好了。










#include<cstdio>

#include<cstring>

int a[100005];

int gcd(int c,intd){

    returnd==0?c:gcd(d,c%d);

}

int main(){

    intT;

    scanf("%d",&T);

    while(T--){

        intn;

        memset(a,0,sizeof(a));

        scanf("%d",&n);

        scanf("%d",&a[0]);

        intlogo=0;

        intasn=a[0];

        for(inti=1;i<n;i++)

        {

            scanf("%d",&a[i]);

            asn=gcd(asn,a[i]);

 

        }

        if(asn==1)

            printf("%d\n",n);

        elseprintf("-1\n");

 

    }

return0;}