D. Integers Have Friends

https://codeforc.es/contest/1549/problem/D

差分 gcd

st 尺取/二分

#include<bits/stdc++.h>
#define inf 1e18
#define ll long long 
#define ull unsigned long long 
#define int long long
#define PI acos(-1.0)
using namespace std;
const int N= 2e5+7;
const int p= 998244353;

int lg[N],a[N],gg[N][50],n,q,b[N];

int query(int l,int r){
    int len=lg[r-l+1];
    int ans=__gcd(gg[l][len],gg[r-(1<<(len))+1][len]);
    return ans;
}

void solve(){
    lg[0]=-1;
       scanf("%lld",&n);
    for(int i=1;i<=n;i++){
        scanf("%lld",&a[i]);
    }
    n--;
    for(int i=1;i<=n;i++){
        b[i]=abs(a[i]-a[i+1]); 
        //printf("%lld ",b[i]);
        lg[i]=lg[i/2]+1;
    }
    //printf("\n");
    for(int i=1;i<=n;i++)
    {
        gg[i][0]=b[i];
    }
    for(int i=1;i<=lg[n];i++)
    {
        for(int j=1;j+(1<<i)-1<=n;j++)
        {
            gg[j][i]=__gcd(gg[j][i-1],gg[j+(1<<(i-1))][i-1]);
        }
    }
    
    int pos=1,ans=0;
    for(int i=1;i<=n;++i){
        while(query(pos,i)==1&&pos<=i)pos++;//考虑到值本身就是1的情况 必须让pos向前消去影响 
        //printf("%lld %lld\n",pos,i);
        ans=max(ans,i-pos+1);
    }
    printf("%lld\n",ans+1);
}
signed main(){
    int t=1;
       scanf("%lld",&t);
    while(t--){
        solve();
    }
    return 0;
}