新思路

一种思路

两个循环分别储存左右abc 125

#include <iostream>
#include<algorithm>
#include <stdio.h>
#include <string>
#include <map>
//#include <bits/stdc++.h>
using namespace std;
/*inline int read(){
    int s=0,w=1;
    char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-')w=-1;ch=getchar();}
    while(ch>='0'&&ch<='9') s=s*10+ch-'0',ch=getchar();
    return s*w;
}*/
typedef long long ll;
int gcd(int a,int b)
{
    return b?gcd(b,a%b):a;
}
int a[100004],b[100004],k[1000001];
int main() {
    int n;
    while (cin >> n) {
        for (int i = 1; i <= n; i++)
            cin >> k[i];
        a[1] = 0, b[n] = 0;
        for (int i = 2; i <= n; i++)
            a[i] = gcd(a[i - 1], k[i - 1]);
        for (int i = n - 1; i >= 1; i--)
            b[i] = gcd(b[i + 1], k[i + 1]);
        int ans = -999;
        for (int i = 1; i <= n; i++)
          ans=max(ans,gcd(a[i],b[i]));
    cout<<ans<<endl;
}
    return 0;
}