HDU 2136 Largest prime factor

Largest prime factor

Time Limit: 5000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 3947    Accepted Submission(s): 1385

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

12345

 

Sample Output

01213

 

题意：就是求一个数能整除它的最大素数的表的位置。

 

AC代码：

#include <stdio.h>int rank[1100000]; int main() {    int n,cnt=1;     for(int i=2;i<1000001;i++)     {        if(rank[i])continue;         for(int j=i;j<1000001;j+=i)             rank[j]=cnt;        cnt++;    }    while(~scanf("%d",&n))         printf("%d\n",rank[n]);     return 0; }