Largest prime factor

最新推荐文章于 2018-05-22 22:23:29 发布

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#ACM #水题 #素数表

本文介绍了一个求解特定数字最大质因数位置的问题，包括输入格式、输出要求及解决算法。

Largest prime factor

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

Total Submission(s): 3288 Accepted Submission(s): 997

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

Sample Output

Author

Wiskey

Source

HDU 2007-11 Programming Contest_WarmUp

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威士忌

#include<cstdio>
#include<iostream>
#include<cstring>
#include<algorithm>
using namespace std;
#define N 1000000
int a[N];
void prime_list()
{
    int i,j,k;
    memset(a,0,sizeof(a));
    for(i=2,k=1;i<N;i++)
    {
        if(!a[i])
        {
            for(j=1;i*j<N;j++)
            {
                a[i*j]=k;
            }
            k++;
        }
    }
}


int main()
{
    int n;
    prime_list();
    while(~scanf("%d",&n))
    {
        printf("%d\n",a[n]);
    }
	return 0;
}