【HDU2136】 Largest prime factor

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. 

InputEach line will contain one integer n(0 < n < 1000000). 

OutputOutput the LPF(n). 

Sample Input

1
2
3
4
5

Sample Output

0
1
2
1
3

/**
素数筛法，每遍历一个外层点时
将它的所有倍数全部赋值为num(当前质因子的序号)
从小到大逐个遍历
4000
即为最大质因子的序号
*/
#include<iostream>
#include<algorithm>
#include<cstring>
#include<cmath>
#include<cstdio>
#include<queue>
#include<vector>
using namespace std;
const int Max = 1e6 + 5;
int n;
int a[Max];
int main()
{
memset(a, 0, sizeof(a));
int num = 1;                        //质因子序号
for(int i = 2; i <= Max; i++)
{
if(!a[i])
{
for(int j = i; j <= Max; j += i)            //i的所有倍数都被赋值为同一个序号
{
a[j] = num;
}
num++;
}
}
while(scanf("%d", &n) != EOF)
{
printf("%d\n", a
);
}
return 0;
}