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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
Source
1 #include<iostream> 2 #include<cstdio> 3 #include<cstring> 4 #include<queue> 5 #include<algorithm> 6 #include<stdlib.h> 7 using namespace std; 8 #define ll long long 9 ll eular(ll n){ 10 ll ans=1; 11 for(ll i=2;i*i<=n;i++){ 12 if(n%i==0){ 13 ans*=i-1,n/=i; 14 while(n%i==0){ 15 ans*=i; 16 n/=i; 17 } 18 } 19 } 20 if(n>1) ans*=n-1; 21 return ans; 22 } 23 int main() 24 { 25 ll n; 26 while(scanf("%I64d",&n)==1){ 27 if(n==0) break; 28 ll ans=eular(n); 29 printf("%I64d\n",ans); 30 } 31 return 0; 32 }
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原文地址：http://www.cnblogs.com/UniqueColor/p/4771271.html
