原题地址:http://acm.hdu.edu.cn/showproblem.php?pid=5901 题意:输入n,输出n以内质数个数 模板题,模板我看不懂,只是存代码用. 官方题解链接:https://async.icpc-camp.org/d/560-2016 /************************************************************ 这个模板我一点都不会,代码是从codeforces上抄的,佚名 pi(i)表示i以内质数的个数 ******…

Count primes 题目连接: http://acm.split.hdu.edu.cn/showproblem.php?pid=5901 Description Easy question! Calculate how many primes between [1...n]! Input Each line contain one integer n(1 <= n <= 1e11).Process to end of file. Output For each case, output…

原题地址:http://acm.hdu.edu.cn/showproblem.php?pid=5881 Tea Time Limit: 3000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others) Total Submission(s): 451    Accepted Submission(s): 124 Problem Description Tea is good. Tea is life. Tea is e…

链接:传送门 题意:计算 [ 1 , n ] 之间素数的个数,(1 <= n <= 1e11) 思路:Meisell-Lehmer算法是计算超大范围内素数个数的一种算法,原理并不明白,由于英语太渣看不懂WIKI上的原理,附WIKI链接:Here /************************************************************************* > File Name: hdu5901.cpp > Author: WArobot &g…

Count primes Time Limit: 12000/6000 MS (Java/Others)    Memory Limit: 65536/65536 K (Java/Others)Total Submission(s): 2625    Accepted Submission(s): 1337 Problem Description Easy question! Calculate how many primes between [1...n]!   Input Each line…

题目链接 http://acm.hdu.edu.cn/showproblem.php?pid=5900 Problem Description Every school has some legends, Northeastern University is the same. Enter from the north gate of Northeastern University,You are facing the main building of Northeastern Universi…

题目链接 题意:求[1,n]有多少个素数,1<=n<=10^11.时限为6000ms. 官方题解:一个模板题, 具体方法参考wiki或者Four Divisors. 题解:给出两种代码. 第一种方法Meisell-Lehmer算法只需265ms. 第二种方法不能运行但是能AC,只需35行. 第一种: //Meisell-Lehmer #include<cstdio> #include<cmath> using namespace std; #define LL long…

题意: 计数区间$[1, n](1 \leq n \leq 10^{11})$素数个数. 分析: 这里只介绍一种动态规划的做法. 首先要说一下[分层思想]在动态规划中非常重要,下面的做法也正是基于这一思想. 我们用$dp[i]$表示区间$[1, \frac{n}{i}]$中素数的个数,用$c[i]$表示区间$[1, i]$中素数个数. 那么我们要求的即是$dp[1]$.由于$n$最大是$10^{11}$,因此任何区间内合数的最小素因子不超过$\sqrt{10^{11}}$.为了筛选素数,只需从区…

转自:http://blog.csdn.net/chaiwenjun000/article/details/52589457 计从1到n的素数个数 两个模板 时间复杂度O(n^(3/4)) #include <bits/stdc++.h> #define ll long long using namespace std; ll f[],g[],n; void init(){ ll i,j,m; ;m*m<=n;++m)f[m]=n/m-; ;i<=m;++i)g[i]=i-; ;i…

#include<cstdio> #include<cmath> using namespace std; #define LL long long ; bool np[N]; int prime[N], pi[N]; int getprime() { ; np[] = np[] = true; pi[] = pi[] = ; ; i < N; ++i) { if(!np[i]) prime[++cnt] = i; pi[i] = cnt; ; j <= cnt &am…