【hdoj2136】Largest prime factor

最新推荐文章于 2020-02-19 15:33:06 发布

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#素数打表

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本文介绍了一种通过打表法快速求解任意整数的最大质因数在其质数序列中位置的算法，并提供了一个完整的C++实现示例。

Largest prime factor

Time Limit: 5000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 11191 Accepted Submission(s): 3961

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

Recommend

威士忌

打表法求一个数的质因数在质数序列中的位置。

#include<cstdio>
#include<iostream>
#include<cstring>
#include<cmath>
#include<algorithm>
using namespace std;
const int MAXN = 1000010;
int vis[MAXN];
void getvis() {
	int k=1;
	for(int i=2; i<=MAXN; i++) {
		if(!vis[i]) {
			vis[i]=k;
			for(int j=i+i; j<=MAXN; j+=i) {
				vis[j]=k;
			}
			k++;
		}
	}
}
int main() {
	getvis();
	int n;
	while(scanf("%d",&n)!=EOF) {
		printf("%d\n",vis[n]);
	}
	return 0;
}