hdu 1695 GCD（容斥）

题目链接

复制代码

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
inline int read()
{
    int x=0,f=1;char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
    while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
    return x*f;
}

/********************************************************************/

const int maxn = 1e5+7;
vector<int> pri[maxn];

//分解成的质数
void init(){
    for(int i = 2;i < maxn; i++){
        int now = i;
        for(int j = 2;j*j <= now;j++){
            if(now%j == 0){
                pri[i].push_back(j);
                while(now%j == 0) now /= j;
            }
            if(now == 1) break;
        }
        if(now > 1)
            pri[i].push_back(now);
    }
}

int solve(int x, int pos){
    int res = 0;
    for(int i = 1;i < (1 << pri[x].size());i++){
        int num = 0;
        int tmp = 1;
        for(int j = 0;j < pri[x].size();j++){
            if((i >> j)& 1){
                num++;
                tmp *= pri[x][j];
            }
        }
        if(num & 1) res += pos/tmp;
        else res -= pos/tmp;
    }
    return pos - res;
}

int main(){
    init();
    int t;
    t = read();
    for(int i = 1;i <= t;i++){
        int a, b, c, d, k;
        //a = 1, d = 1;
        a = read(); b = read(); c = read(); d = read(); k = read();
        if(k == 0){
            printf("Case %d: 0\n", i);
            continue;
        }
        b /= k, d /= k;
        if(b < d) swap(b, d);
        ll ans = 0;
        for(int j = 1;j <= b;j++){
            ans += solve(j, min(j, d));
        }
        printf("Case %d: %lld\n", i, ans);
    }
    return 0;
}