HDOJ 2136 Largest prime factor

Largest prime factor

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

Total Submission(s): 9250 Accepted Submission(s): 3268



[align=left]Problem Description[/align]
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.

[align=left]Input[/align]
Each line will contain one integer n(0 < n < 1000000).

[align=left]Output[/align]
Output the LPF(n).

[align=left]Sample Input[/align]

1
2
3
4
5

[align=left]Sample Output[/align]

0
1
2
1
3

[align=left]Author[/align]
Wiskey

[align=left]Source[/align]
HDU 2007-11 Programming Contest_WarmUp

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很有意思的一道题，更加理解素数打表原理。

前两天做的好像没传上来，今天扔上来。

#include<stdio.h>
#include<string.h>
#define Max 1000001
int a[Max];
void S()
{
int i,j;
int k=1;
memset(a,0,sizeof(a));
for(i=2;i<Max;i++)
{
if(!a[i])
a[i]=k++;
for(j=i+i;j<Max;j+=i)
a[j]=a[i];
}
}
int main()
{
S();
int n;
while(~scanf("%d",&n))
printf("%d\n",a
);
return 0;
}