hdu 1695 GCD（容斥）

题目链接

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

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

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

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

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

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