hdu 2136

Largest prime factor

Time Limit: 5000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 4409    Accepted Submission(s): 1560

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

 

Source

HDU 2007-11 Programming Contest_WarmUp

 

Recommend

威士忌

 

//素数倍数一起置为它的素数序号，这样数组里存放的序号就是最大素数因子的序号了
#include <stdio.h>
#include <string.h>
int a[1000001];
int main()
{
	int n, num = 1, i, j;
	memset(a, 0, sizeof(a));
	for(i = 2; i < 1000001; i++)
	{
		if(a[i])
			continue;
		else
			for (j = i; j < 1000001; j += i)
				a[j] = num;
		num++;
	}
	while(~scanf("%d", &n))
		printf("%d\n", a[n]);
	return 0;
}