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POJ 2407 Relatives(欧拉函数入门题)

时间:2018-07-29 22:32:47      阅读:180      评论:0      收藏:0      [点我收藏+]

标签:lin   def   tps   namespace   positive   space   target   problem   stand   

Relatives

Given n, a positive integer, how many positive integers less than n are relatively prime to n? Two integers a and b are relatively prime if there are no integers x > 1, y > 0, z > 0 such that a = xy and b = xz.

Input

There are several test cases. For each test case, standard input contains a line with n <= 1,000,000,000. A line containing 0 follows the last case.

Output

For each test case there should be single line of output answering the question posed above.
 
Sample Input
7
12
0
Sample Output
6
4

题意:输入个n,求(1,n-1)与n互质的个数有多少个
思路:这明显就是欧拉函数模版题,就是求n的欧拉数
#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
using namespace std;
typedef long long ll;
ll phi(ll n)//求n的欧拉数
{
    ll sum=n;
    for(int i=2;i*i<=n;i++)//O(根号n的复杂度)
    {
        if(n%i==0)
        {
            sum=sum-sum/i;
            do
            {
                n/=i;
            }while(n%i==0);
        }
    }
    if(n>1) sum=sum-sum/n;
    return sum;
}
int main()
{
    ll n;
    while(scanf("%lld",&n)!=EOF)
    {
        if(n==0)
        break;
        printf("%lld\n",phi(n));
    }
}

 

 

POJ 2407 Relatives(欧拉函数入门题)

标签:lin   def   tps   namespace   positive   space   target   problem   stand   

原文地址:https://www.cnblogs.com/Lis-/p/9387619.html

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