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  1. #include <stdio.h>
  2. #include <stdbool.h>
  3. #include <math.h>
  4.  
  5. int power(int a, int b, int c) {
  6.     int result = 1;
  7.     while (b > 0) {
  8.         if (b % 2 == 1)
  9.             result = (result * a) % c;
  10.         b /= 2;
  11.         a = (a * a) % c;
  12.     }
  13.  
  14.     return result;
  15. }
  16.  
  17. bool is_prime(int n) {
  18.     if (n < 2)
  19.         return false;
  20.     if(n == 2)
  21. 	    return true; 
  22.  
  23.     for (int k = 2; k <= sqrt(n); k++) {
  24.         if (n % k == 0)
  25.             return false;
  26.     }
  27.  
  28.     int a = 2;
  29.     if (power(a, n-1, n) != 1)
  30.         return false;
  31.  
  32.     return true;
  33. }
  34.  
  35. int main() {
  36.     int n;
  37.     printf("Nhap mot so nguyen duong: ");
  38.     scanf("%d", &n);
  39.  
  40.     if (is_prime(n))
  41.         printf("%d la so nguyen to.\n", n);
  42.     else
  43.         printf("%d la hop so.\n", n);
  44.  
  45.     return 0;
  46. }
  47.  
Success #stdin #stdout 0s 5444KB
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Nhap mot so nguyen duong: 32766 la hop so.
https://ideone.com/TZazuI
language:
C (gcc 8.3)
created:
2 years ago
visibility:
public

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