HDU 2136 Largest prime factor

http://acm.hdu.edu.cn/showproblem.php?pid=2136

 

Largest prime factor

Time Limit: 5000/1000 MS(Java/Others)    MemoryLimit: 32768/32768 K (Java/Others)
Total Submission(s):2815    AcceptedSubmission(s): 993

Problem Description

Everybody knows any number can becombined by the prime number.
Now, your task is telling me what position of the largest primefactor.
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 45

 

 

Sample Output

0 1 2 13

 

 

Author

Wiskey

 

 

Source

HDU 2007-11 Programming Contest_WarmUp

 

 

Recommend

威士忌

 

题意：给一个数，求它的最大质因子在素数中的排名。1为0,2为1，3为2……

分析：用哈希打表的方法搞定

代码如下：

#include<stdio.h>
#include<string.h>
int biao[1000001];
void fun()
{
 int i,j,k=1;
 memset(biao,0,sizeof(biao));
 for(i=2;i<1000000;i++)
 {
  if(biao[i]==0)
    {
    for(j=1;i*j<999999;j++)
       biao[i*j]=k;
       k++;
    }
 }
 biao[1]=0;
}
int main()
{
 int n;
 fun();
 while(scanf("%d",&n)!=EOF)
 {
  printf("%d\n",biao[n]);
 }
 return 0;
}