clib.c

#include <stdio.h>

int result_c (int max_a0, int *max_len_r, int *longest_r) {
   int longest = 0, max_len = 0;
   int a0, len;
   unsigned long a;
   
   for (a0 = 1; a0 <= max_a0; a0++) {
      a = a0;
      len = 0;
      
      while (a != 1) {
         len++;
         a = ((a%2==0)? a : 3*a+1)/2;
      }
      
      if (len > max_len) {
         max_len = len;
         longest = a0;
      }
   }

   *max_len_r = max_len;
   *longest_r = longest;

   /* printf("(%d, %d)\n", max_len, longest); */
   return longest;
}