HDOJ 题目Largest prime factor（水题）

Largest prime factor

Time Limit: 5000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 6858    Accepted Submission(s): 2430

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

12345

 

Sample Output

01213

 

Author

Wiskey

 

Source

HDU 2007-11 Programming Contest_WarmUp

 

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ac代码

#include<stdio.h>#include<string.h>int a[1000005];void fun(){int i,j,k=1;;for(i=2;i<1000005;i++){if(!a[i]){a[i]=k++;for(j=i+i;j<1000005;j+=i)a[j]=a[i];}}}int main(){int n;fun();while(scanf("%d",&n)!=EOF){printf("%d\n",a[n]);}}