HDU 2136 Largest prime factor 数论

最新推荐文章于 2020-02-18 01:08:25 发布

转载最新推荐文章于 2020-02-18 01:08:25 发布 · 45 阅读

0 ·

CC 4.0 BY-SA版权

原文链接：http://www.cnblogs.com/Hyouka/p/5721471.html

本文介绍了一个算法，用于计算任意整数的最大质因数的位置。通过预处理的方法，为每个小于100万的整数标记其最大的质因数对应的质数序列位置，实现了快速查询。

Largest prime factor

Time Limit:1000MS Memory Limit:32768KB 64bit IO Format:%I64d & %I64u

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

0
1
2
1
3

还是预处理

#include <iostream>
#include <cstring>
#include <cstdio>
#include <algorithm>
#include <queue>
#include <vector>
#include <iomanip>
#include <math.h>
using namespace std;
#define FIN     freopen("input.txt","r",stdin);
#define INF     0x3f3f3f3f
#define lson    l,m,rt<<1
#define rson    m+1,r,rt<<1|1
typedef long long LL;

int p[1000005];

int main()
{
    //FIN
    int cou=0;
    for(int i=2; i<=1000000; i++)
    {
        if(p[i]==0)
        {
            cou++;
            for(int j=i; j<=1000000; j=j+i)
            {
                p[j]=cou;
            }
        }
    }

    int n;
    while(~scanf("%d",&n))
    {
        printf("%d\n",p[n]);
    }

}

转载于:https://www.cnblogs.com/Hyouka/p/5721471.html