hdu 2136 Largest prime factor（素数打表）

Larg
4000
est prime factor

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

Total Submission(s): 11131    Accepted Submission(s): 3936


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

#include<cstdio>
#include<cstring>
using namespace std;
const int maxn = 1000005;
int pre[maxn];
void dabiao()
{
int k = 1;
memset(pre,0,sizeof(pre));
for(int i = 2; i < maxn; ++i)
{
if(pre[i] == 0)
{
for(int j = 1; i * j < maxn; ++j)
pre[i*j] = k;
k++;
}
}
}
int main()
{
int n;
dabiao();
while(~scanf("%d",&n))
{
printf("%d\n",pre
);
}
return 0;
}