A chance to brush off my C :)

// inc_c - http://perlmonks.org/?node_id=1128230

#include <stdlib.h>
#include <stdio.h>

#define M 5 // place
#define N 3 // number of elements wanted

static int place[N];

int
step(void)
  {
  for(int i = 0; i < N; i++)
    {
    if(i < N - 1 ? place[i] < place[i + 1] - 1 : place[i] < M - 1 )
      {
      place[i]++;
      for(int j = i - 1; j >= 0; j--) place[j] -= place[0];
      return 1;
      }
    }
  return 0;
  }

int
main(int argc, char **argv)
  {
  int i;
  int more = 1;

  for(i = 0; i < N; i++) place[i] = i;

  while(more)
    {
    for(i = 0; i < N; i++) printf(" %d", place[i]);
    putchar('\n');
    more = step();
    }

  exit(0);
  }
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