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 程式師世界 >> 編程語言 >> C語言 >> C++ >> C++入門知識 >> POJ 2407-Relatives(求一個整數的歐拉函數值)

POJ 2407-Relatives(求一個整數的歐拉函數值)

編輯:C++入門知識

POJ 2407-Relatives(求一個整數的歐拉函數值)


 

Relatives Time Limit:1000MS Memory Limit:65536KB 64bit IO Format:%I64d & %I64u Submit Status Practice POJ 2407 Appoint description:

Description

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

 

題意:給一個數n,求出不大於n且與n互素的數的個數。

 

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include
using namespace std;
typedef long long LL;
const int inf=0x3f3f3f3f;
const double pi= acos(-1.0);

int Euler(int n)
{
    int m=floor(sqrt(n+0.5));
    int ans=n;
    for(int i=2;i<=m;i++){
        if(n%i==0){
            ans=ans/i*(i-1);
            while(n%i==0){
                n/=i;
            }
        }
    }
    if(n>1)
        ans=ans/n*(n-1);
    return ans;
}
int main()
{
    int n;
    while(~scanf("%d",&n)){
        if(!n) break;
        printf("%d\n",Euler(n));
    }
    return 0;
}


 

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