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  1. #include <assert.h>
  2. #include <stdio.h>
  3. #include <stdint.h>
  4. #include <stdlib.h>
  5.  
  6. int ack_recursive(int m, int n) {
  7.     if (m == 0) {
  8.         return n + 1;
  9.     }
  10.  
  11.     if (n == 0) {
  12.         return ack_recursive(m - 1, 1);
  13.     }
  14.  
  15.     return ack_recursive(m - 1, ack_recursive(m, n - 1));
  16. }
  17.  
  18. int ack_nonrecursive(int m, int n, int *status) {
  19.     int *value = NULL;
  20.     size_t size = 0;
  21.  
  22.     while (size >= 0) {
  23.         if (m == 0) {
  24.             n++;
  25.             if (size-- == 0) {
  26.                 *status = EXIT_SUCCESS;
  27.                 break;
  28.             }
  29.             m = value[size];
  30.             continue;
  31.         }
  32.  
  33.         if (n == 0) {
  34.             m--;
  35.             n = 1;
  36.             continue;
  37.         }
  38.  
  39.         size_t index = size++;
  40.         if ((size & index) == 0) {
  41.             if (size >= SIZE_MAX / sizeof *value) {
  42.             	*status = EXIT_FAILURE;
  43.                 break;
  44.             }
  45.  
  46.             void *temp = realloc(value, (2 * size + 1) * sizeof *value);
  47.             if (temp == NULL) {
  48.             	*status = EXIT_FAILURE;
  49.                 break;
  50.             }
  51.  
  52.             value = temp;
  53.         }
  54.  
  55.         value[index] = m - 1;
  56.         n--;
  57.     }
  58.  
  59.     free(value);
  60.     return n;
  61. }
  62.  
  63. int main(void) {
  64.     for (int m = 0; m < 2; m++) {
  65.         for (int n = 0; n < 2; n++) {
  66.             int status;
  67.             assert(ack_recursive(m, n) == ack_nonrecursive(m, n, &status) && status == EXIT_SUCCESS);
  68.         }
  69.     }
  70. }
Success #stdin #stdout 0s 2376KB
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https://ideone.com/IPWV43
language:
C99 (gcc 8.3)
created:
11 years ago
visibility:
public

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