TheAlgorithms-C/sorting/Pigeonhole_Sort.c

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

void pigeonholeSort(int arr[], int size)
{
  int i, j, min = arr[0], max = arr[0], range;

  // Getting range of the array using max and min
  for (i=1; i<size; i++)
  {
    if (arr[i] < min)
      min = arr[i];
    if (arr[i] > max)
      max = arr[i];
  }
  range = max - min + 1;

  // Make 'holes' and put array's numbers in holes
  int * holes = (int*)malloc(sizeof(int) * range);
  for (i=0; i<range; i++)
  {
    holes[i] = 0;
  }
  for (i=0; i<size; i++)
  {
    holes[arr[i] - min]++;
  }

  // Copy the numbers back to the original array
  j=0;
  for (i=0; i<range; i++)
  {
    while (holes[i] > 0)
    {
      arr[j] = i + min;
      holes[i]--;
      j++;
    }
  }

  free(holes);
}

int main()
{
  int i, n;

  printf("Enter the size of the array: ");
  scanf("%d", &n);
  int * arr = (int*)malloc(sizeof(int) * n);

  for (i = 0; i < n; i++)
  {
    printf("Number #%d: ", i + 1);
    scanf("%d", &arr[i]);
  }

  printf("You entered:  ");
  for (i=0; i<n; i++)
  {
    printf("%d ", arr[i]);
  }
  pigeonholeSort(arr, n);
  printf("\nSorted array: ");
  for (i=0; i<n; i++)
  {
    printf("%d ", arr[i]);
  }
  printf("\n");

  free(arr);
  return 0;
}