Largest prime factor

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 3一个数如果是质数，则不可能通过某个数的倍乘去得到它如果不是质数，则可以通过某个小整数的有限次的倍乘得到它

#include<stdio.h>
  #include<string.h>
int a[1000000]; //题意
int main()
 {
     int i,j,k;
     memset(a,0,100000);
for(i=2,k=0;i<1000000;i++)
    {
   if(!a[i]) // 确保每个数都不重复出现
     {
      k++; // 对于未出现的要+1，递推
     for(j=i;j<1000000;j+=i)
               a[j]=k;
  }
 }
 int n;
  while(scanf("%d",&n)!=EOF)
    {
   printf("%d\n",a[n]);
  }
 return 0;
 }