POJ 1284 Primitive Roots
Description
We say that integer x, 0 < x < p, is a primitive root modulo odd prime p if and only if the set { (xi mod p) | 1 <= i <= p-1 } is equal to { 1, ..., p-1 }. For example, the consecutive powers of 3 modulo 7 are 3, 2, 6, 4, 5, 1, and thus 3 is a primitive root modulo 7.
Write a program which given any odd prime 3 <= p < 65536 outputs the number of primitive roots modulo p.
Write a program which given any odd prime 3 <= p < 65536 outputs the number of primitive roots modulo p.
Input
Each line of the input contains an odd prime numbers p. Input is terminated by the end-of-file seperator.
Output
For each p, print a single number that gives the number of primitive roots in a single line.
Sample Input
23 31 79
Sample Output
10 8 24
View Code
1 #include<stdio.h> 2 int getans(int n){ 3 int ans = n; 4 for(int i=2;i<=n;i++) 5 if(n%i==0){ 6 ans = ans / i * (i-1) ; 7 while(n%i==0) n /= i; 8 } 9 if(n > 1) ans = ans/n*(n-1) ; 10 return ans ; 11 } 12 int main(){ 13 int p; 14 while(scanf("%d",&p)!=EOF){ 15 printf("%d\n",getans(p-1)); 16 } 17 return 0; 18 }