hdu 6428 Calculate

题解

#include"bits/stdc++.h"
using namespace std;
typedef long long LL;
const int MX = 1e7+7;
const int mod = 1<<30;
bool no_prime[MX];
int prime[MX],f[2][MX],h[MX],tail;

void init()
{
    int n = 1e7;
    f[0][1] = f[1][1] = 1, h[1] = 1;
    for(int i = 2; i<= n; i++){
        if(!no_prime[i]){
            prime[++tail] = i;
            f[0][i] = f[1][i] = i;
            h[i] = i-2;
        }
        for(int j = 1; j <= tail; j++){
            int x = i*prime[j];
            if(x > n) break;
            no_prime[x] = 1;

            int p = prime[j];
            if(i % p == 0){
                int temp = i;
                int cnt = 1;
                while(cnt < 3 && temp % p == 0) temp /= p, ++cnt;

                f[0][x] = f[0][i/p]*p;

                if(cnt == 2) f[1][x] = f[1][i/p]*p;
                else f[1][x] = f[1][i/p/p]*p;

                if(cnt == 2) h[x] = h[i/p]*(p-1)*(p-1);
                else h[x] = h[i]*p;

                break;
            }
            f[0][x] = f[0][i]*p;
            f[1][x] = f[1][i]*p;
            h[x] = h[i]*(p - 2);
        }
    }
}

void upd(LL &a, LL b)
{
    a = (a+b)%mod;
}

void solve()
{
    int a,b,c;
    scanf("%d%d%d",&a,&b,&c);
    LL ans = 0;
    for(int i = 1; i <= a; i++){
        upd(ans,1LL*h[i]*(a/i)%mod *(b/f[0][i])%mod *(c/f[1][i])%mod);
    }
    printf("%lld\n",ans);
}

int main()
{
    int T;
    init();
    cin>>T;
    while(T--) solve();
    return 0;
}