gcd_difference

bruteforce for https://oeis.org/A199768
git clone https://a3nm.net/git/gcd_difference/
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main.c (828B)

      1 #include<stdio.h>
      2 #include<stdbool.h>
      3 #include<stdlib.h>
      4 
      5 // bruteforce https://oeis.org/A213918
      6 
      7 int res[10];
      8 int num = 0;
      9 
     10 bool ok(int i, int found) {
     11   for (int j = 0; j < found; j++) {
     12     if (res[j] % (i - res[j]))
     13       return false;
     14   }
     15   return true;
     16 }
     17 
     18 bool search(int ci, int maxi, int found, int tofind) {
     19   if (found == tofind)
     20     return true;
     21   for (int i = ci+1; i < maxi; i++) {
     22     if (!ok(i, found))
     23       continue;
     24     res[found] = i;
     25     if (search(i, maxi, found+1, tofind))
     26       return true;
     27   }
     28   return false;
     29 }
     30 
     31 int main(int argc, char **argv) {
     32   int k = atoi(argv[1]);
     33   int n = atoi(argv[2]);
     34   res[0] = 0;
     35   if (search(0, k, 1, n)) {
     36     printf("solution found:\n");
     37     for (int i = 0; i < n; i++)
     38       printf("%d ", res[i]);
     39     printf("\n");
     40   } else {
     41     printf("nothing found :(\n");
     42   }
     43 }
     44