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  1. // Factorial. (2.00)
  2.  
  3. #include <limits.h>
  4. #include <errno.h>
  5. #include <string.h>
  6. #include <stdio.h>
  7.  
  8. static inline _Bool mul_overflow(int a, int b, int *c)
  9. {
  10.     if (a != 0 && INT_MAX/a < b)
  11.         return 1;
  12.     *c = a*b;
  13.     return 0;
  14. }
  15.  
  16. int factorial(int n)
  17. {
  18.     if (n < 0)
  19.     {
  20.         errno = EDOM;
  21.         return -1;
  22.     }
  23.  
  24.     int result = 1;
  25.  
  26.     while (n > 1)
  27.     {
  28.         if (mul_overflow(n, result, &result))
  29.         {
  30.             errno = ERANGE;
  31.             return -1;
  32.         }
  33.         n -= 1;
  34.     }
  35.     return result;
  36. }
  37.  
  38. int main(void)
  39. {
  40.     for (int i = -1; i < 14; i++)
  41.     {
  42.         int result = factorial(i);
  43.         if (result < 0)
  44.             printf("%2d! : %s\n", i, strerror(errno));
  45.         else
  46.             printf("%2d! = %d\n", i, result);
  47.     }
  48.     return 0;
  49. }
Success #stdin #stdout 0s 5320KB
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stdout
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-1! : Numerical argument out of domain
 0! = 1
 1! = 1
 2! = 2
 3! = 6
 4! = 24
 5! = 120
 6! = 720
 7! = 5040
 8! = 40320
 9! = 362880
10! = 3628800
11! = 39916800
12! = 479001600
13! : Numerical result out of range
https://ideone.com/gnevsJ
language:
C (gcc 8.3)
created:
2 days ago
visibility:
public

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