Find duplicates

Find duplicates

Given an array of n elements which contains elements from 0 to n-1, with any of these numbers appearing any number of times.

#include <stdio.h>

#include <stdlib.h>

void printRepeating(int arr[], int size)                                                

{

  int i;

  printf("The repeating elements are: \n");

  for (i = 0; i < size; i++)

  {

    if (arr[abs(arr[i])] >= 0)

      arr[abs(arr[i])] = -arr[abs(arr[i])];

    else

      printf(" %d ", abs(arr[i]));

  }

}

int main()

{

  int arr[] = {1, 2, 3, 1, 3, 6, 6};

  int arr_size = sizeof(arr)/sizeof(arr[0]);

  printRepeating(arr, arr_size);

  getchar();

  return 0;

}

Output:

The repeating elements are:

1  3  6