mnaydin

  int (*ap3)[900000] = malloc(sizeof *ap3);

  int *a = malloc(900000 * sizeof *a);

  while (1) {
    calc(x++);
  }

    Blank     One line
      0       Two lines
      1       To first line of next page
      +       No advance

  cat sales.csv | awk -F',' '{print $1}'

  cut -d, -f1 sales.csv

  cat sales.csv | awk -F',' '{print $1}' | sort | uniq

  cut -d, -f1 sales.csv | sort -u

  mid = ((unsigned int)low + (unsigned int)high)) >> 1;

  for (size_t i = len; i > 0; --i) {
     // use i-1 as the array index
  }

  size_t i = len
  while (i-- > 0) {
    // use i as the array index
  }

  ls -1 | uniq -u -w4