Largest prime factor

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

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

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的序号为3，以此类推。现在要求输出所

给定的数n的最大质因子的序号，0<n<1000000。

#include<iostream>
#include<stdio.h>
using namespace std;
int pi;
bool flag[1000010];
int in;
int n;
int a[1000010];
int getprime()
{
    for(int i=2;i<1000010;++i)
    {
        if(!flag[i])
        {
            in++;
            for(int j=i;j<1000010;j+=i)
            {
                flag[j]=true;
                a[j]=in;//记录序号
            }
        }
    }
}
int main(int argc, char *argv[])
{
    //freopen("2136.in","r",stdin);
    getprime();
    while(scanf("%d",&n)!=EOF)
    {
        printf("%d\n",a[n]);
    }
    return 0;
}