GCD

Posted 2021-02-15 acm1ruoji

题目传送门：

#include <cstdio>
#include <cmath>
#include <cstring>
#include <string>
#include <cstdlib>
#include <sstream>
#include <iostream>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <algorithm>
#include <functional>
using namespace std;
#define ll long long
#define re register
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define P pair<int,int>
void read(int &a)
{
    a=0;
    int d=1;
    char ch;
    while(ch=getchar(),ch>‘9‘||ch<‘0‘)
        if(ch==‘-‘)
            d=-1;
    a=ch-‘0‘;
    while(ch=getchar(),ch>=‘0‘&&ch<=‘9‘)
        a=a*10+ch-‘0‘;
    a*=d;
}
void write(int x)
{
    if(x<0)
        putchar(45),x=-x;
    if(x>9)
        write(x/10);
    putchar(x%10+‘0‘);
}
ll euler(ll x)
{
    ll ans=x;
    if(x%2==0)
    {
        while(x%2==0)
            x/=2;
        ans/=2;
    }
    for(re int i=3;i*i<=x;i+=2)
    {
        if(x%i==0)
        {
            while(x%i==0)
                x/=i;
            ans=ans/i*(i-1);
        }
    }
    if(x>1)
        ans=ans/x*(x-1);
    return ans;
}
int main()
{
    int T;
    read(T);
    while(T--)
    {
        ll a,b;
        ll ans=0;
        scanf("%lld %lld",&a,&b);
        if(b==1)
        {
            printf("%lld
",a);
            continue;
        }
        for(re ll i=2;i<=sqrt(a);i++)
            if(a%i==0)
            {
                if(i>=b)
                    ans+=euler(a/i);
                if(a/i>=b)
                    ans+=euler(i);
            }
        int x=sqrt(a+0.5);
        if(x*x==a&&x>=b)///防止加两次
            ans-=euler(x);
        printf("%lld
",ans+1);///加上gcd(a,a)的情况，因为a>=b，所以不需要特判
    }
    return 0;
}