Largest prime factor

Time Limit: 5000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)

Total Submission(s): 6990    Accepted Submission(s): 2471

Problem Description
Everybody knows any number can be combined by the prime number.

Now, your task is telling me what position of the largest prime factor.

The position of prime 2 is 1, prime 3 is 2, and prime 5 is 3, etc.

Specially, LPF(1) = 0.
 
Input
Each line will contain one integer n(0 < n < 1000000).
 
Output
Output the LPF(n).
 
Sample Input
1
2
3
4
5
 
Sample Output
0
1
2
1
3
 
Author
Wiskey
 
Source
 
Recommend
威士忌   |   We have carefully selected several similar problems for you:  2133 2135 1215 2137 2134 
 

我的思路 先打了素数表 再用二分查找去找最大的素数。。结果果断TLE了

代码在此:

#include<stdio.h>
int YNprime[1000001];
int prime[200000];
int totprime=1;
int getprime(int maxN)
{
int i,j,k;
for(i=2;i<=maxN;i++)
if(YNprime[i]==0)
{
prime[totprime++]=i;
for(j=2;i*j<=maxN;j++)
YNprime[i*j]=1;
}
return 1;
}
int find(int s,int t,int N)
{
int i;
int m=(s+t)/2;
if(s==t) return s;
if(prime[m]>N) return find(s,m,N);
if(prime[m]<N) return find(m+1,t,N);
else return m;
}
int main()
{
freopen("a.in","r",stdin);
freopen("a.out","w",stdout);
int n,i,ans,k;
getprime(1000000);
while(scanf("%d",&n)!=EOF)
{
ans=0;
if(n==1) {printf("0\n");continue;}
k=find(1,totprime-1,n);
for(i=k+10;i>=1;i--)
if(n%prime[i]==0) {ans=i;break;}
printf("%d\n",ans);
}
return 0;
}

结果发现沙茶了

筛选法的时候就能直接找最大的素数

#include <cstdio>
#include <iostream> using namespace std; #define Maxl 1000005
int prime[Maxl];
int rank[Maxl];
int main()
{
int k = 0, i, j;
for (i =2; i < Maxl; i++)
{
if (prime[i] == 0)
{
rank[i] = ++k;
for (j = i; j < Maxl; j += i)
{
prime[j] = i;
}
}
}
prime[1] = 0;
int n;
while(scanf("%d", &n) == 1)
{
if(n == 1)
{
printf("0\n");
continue;
}
int k = prime[n];
printf("%d\n", rank[k]);
}
}

【沙茶了+筛选保存最大质因数】【HDU2136】Largest prime factor的更多相关文章

  1. [暑假集训--数论]hdu2136 Largest prime factor

    Everybody knows any number can be combined by the prime number. Now, your task is telling me what po ...

  2. [HDU2136] Largest prime factor(素数筛)

    传送门 题意 给出若干个数n(n<=1000000),求每个n的最大质因子的排名. 质数的排名:如果素数p是第k小的素数,那么p的排名就是k. 思路 乍一看不知道怎么搞. 其实可以想想我们怎么筛 ...

  3. 数学--数论--HDU2136 Largest prime factor 线性筛法变形

    Problem Description Everybody knows any number can be combined by the prime number. Now, your task i ...

  4. The largest prime factor(最大质因数)

    1. 问题: The prime factors of 13195 are 5, 7, 13 and 29.What is the largest prime factor of the number ...

  5. R语言学习——欧拉计划(3)Largest prime factor 求最大质因数

    The prime factors of 13195 are 5, 7, 13 and 29. What is the largest prime factor of the number 60085 ...

  6. HDU 2136 Largest prime factor(查找素数,筛选法)

    题目梗概:求1000000以内任意数的最大质因数是第几个素数,其中 定义 1为第0个,2为第1个,以此类推. #include<string.h> #include<stdio.h& ...

  7. HDOJ(HDU) 2136 Largest prime factor(素数筛选)

    Problem Description Everybody knows any number can be combined by the prime number. Now, your task i ...

  8. hdu-2136 Largest prime factor---巧用素数筛法

    题目链接: http://acm.hdu.edu.cn/showproblem.php?pid=2136 题目大意: 每个素数在素数表中都有一个序号,设1的序号为0,则2的序号为1,3的序号为2,5的 ...

  9. HDU-4690 EBCDIC 映射,模拟,沙茶

    题目链接:http://acm.hdu.edu.cn/showproblem.php?pid=4690 纯沙茶模拟题... //STATUS:C++_AC_93MS_228KB #include &l ...

随机推荐

  1. Android系统进程间通信(IPC)机制Binder中的Client获得Server远程接口过程源代码分析

    文章转载至CSDN社区罗升阳的安卓之旅,原文地址:http://blog.csdn.net/luoshengyang/article/details/6633311 在上一篇文章中,我 们分析了And ...

  2. Swift学习之类和结构体的创建

    随着一步步的学习,学习到的新知识越来越多了,不管是新的还是旧的,都禁不住时间的堆积,再熟悉的知识点时间久了都会渐渐的忘记,也许这就是人们生活中一种潜在的惰性吧,看似非常熟悉的东西,等到真正要用的时候, ...

  3. CSS的优先级

    样式的优先级: (内联样式表[嵌入式样式])>(内部样式表)>(外部样式表) 经过测试动手测试发现有个(唯一的)例外 情况:当引用外部样式在内部样式表(非嵌入式样式)的后面时,外部样式会覆 ...

  4. 动态设置Head的Title、Descrption

    HtmlMeta desc = new HtmlMeta(); desc.Name = "Description"; desc.Content = strTitle.ToStrin ...

  5. Android Studio添加应用作为依赖时报错Error:Dependency MonthText:xlistview:unspecified on project app resolves to an APK archive which is not supported as a compilation dependency. File: 及其解决方案

    Error:Dependency MonthText:xlistview:unspecified on project app resolves to an APK archive which is ...

  6. iOS 面试基础题

    1.UIWindow和UIView和 CALayer 的联系和区别? 答:UIView是视图的基类,UIViewController是视图控制器的基类,UIResponder是表示一个可以在屏幕上响应 ...

  7. 如何更改 Mac OS X 系统默认用户名

    说到 Mac 用户名估计有许多人都不知道在哪个地方修改,其实说简单也简单说麻烦也麻烦看你自己的需求.好比如果你只要用户名的登录更改,那是就非常简单的事了.下面这里就给大家介绍mac osx系统如何更改 ...

  8. C#中Dispose、析构函数、close的区别

    一.Close与Dispose这两种方法的区别 调用完了对象的Close方法后,此对象有可能被重新进行使用:而Dispose方法来说,此对象所占有的资源需要被标记为无用了,也就是此对象要被销毁,不能再 ...

  9. php 大流量网站访问

    1:确认服务器硬件能否支持当前流量 2:数据库优化,用到什么字段查什么字段,减轻查询负担. 3:静态化,缓存,减少连库操作. 4:禁止外部盗链,减轻负载压力. 5:控制文件下载大小,尽量不超过2M,有 ...

  10. 写入和读取LOB类型的对象

    ====写入数据============ create or replace procedure addWaterFallis directions clob; amount binary_integ ...