Codeforces Round #691 (Div. 2) C. Row GCD

Meaning of the question:
Given two arrays a, b, for each number in the b array, find gcd(a[1]+b[j],a[2]+b[j],a[3]+b [j],…).

Solution:
This question mainly examines the nature of gcd, if you know it, you can go directly to the second. The properties are as follows:
gcd(a[1],a[2],a[3],a[4],...)=gcd(a[1],a[2]-a[1],a[3]- a[2],a[4]-a[3],...).
Then the formula for the title becomes gcd(a[1]+b[j],a[2]-a[1],a[3]-a[2],a[4]-a[3] ,...)
So we first preprocess gcd(a[2]-a[1],a[3]-a[2],a[4]-a[3],...). Finally, enumerate for the answer.
Note: Sort before preprocessing, otherwise there may be negative numbers in subtraction.

Code:

#include<bits/stdc++.h>
#include<cstdio>
#include<iostream>
#include<algorithm>
#include<cstring>
#include<cmath>
#include<queue>
#include<map>
#include<stack>
#include<set>
#define iss ios::sync_with_stdio(false)
using namespace std;
typedef unsigned long long ull;
typedef long long ll;
typedef pair<int,int>pii;
const int MAXN=2e5+5;
const int mod=77797;
ll a[MAXN];
ll b[MAXN]; 
ll gcd(ll x,ll y)
{
    
    
    return y?gcd(y,x%y):x;
}
int main()
{
    
    
    int n,m;
    cin>>n>>m;
    for(int i=1;i<=n;i++)
    {
    
    
        cin>>a[i];
    }
    sort(a+1,a+1+n);
    for(int i=1;i<=m;i++)
    {
    
    
        cin>>b[i];
    }
    if(n==1)
    {
    
    
        for(int i=1;i<=m;i++)
        {
    
    
            printf("%lld ",b[i]+a[1]);
        }
    }
    else
    {
    
    
        ll gd=a[n]-a[n-1];
        for(int i=n-1;i>=2;i--)
        {
    
    
            gd=gcd(gd,a[i]-a[i-1]);
        }
        for(int i=1;i<=m;i++)
        {
    
    
            ll gg=gd;
            gg=gcd(gg,a[1]+b[i]);
            printf("%lld ",gg); 
        }
    }
}

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Origin blog.csdn.net/weixin_45755679/article/details/113406857