vijos1889：天真的因数分解

题目链接

vijos1889：天真的因数分解

题解

同bzoj2440: [中山市选2011]完全平方数

就是改成了求有平方因子数,依旧考虑二分，只是把容斥系数取一下相反数,也就是把莫比乌斯函数求一个反着的

详见上方题解链接

代码

#include<cmath>
#include<cstdio>
#include<algorithm>
const int maxn = 200007;
#define int long long
inline int read() {
	int x = 0;
	char c = getchar();
	while(c < '0' || c > '9') c = getchar();
	while(c <= '9' && c >= '0') x = x * 10 + c - '0',c = getchar();
	return x;
}
int prime[maxn],mu[maxn];bool p[maxn];
void get_mu() {
	//mu[1] = 1;
	int n = maxn - 7,num = 0;
	for(int i = 2;i <= n;++ i) {
		if(!p[i]) prime[++num] = i,mu[i] = 1;
		for(int j = 1;j <= num && prime[j] * i <= n;++ j) {
			p[i * prime[j]] = 1;
			if(i % prime[j] == 0) break;
			mu[i * prime[j]] = -mu[i];
		}
	}
}
int check(int x) {
	int ret = 0 ;
	for(int i = 2;i <= sqrt(x); ++ i ) {
		ret += mu[i] * (x / (i * i));
	}
	return ret;
}
main() {
	get_mu();
	int k = read();
	int l = 1,r = 30000000000,ans;
	//	if(k == 1)puts("1");
	while(l <= r) {
		int mid = l + r >> 1;
		if(check(mid) >= k) ans = mid,r = mid - 1;
		else l = mid + 1;
	}
	printf("%lld\n",ans);
	return 0;
}