Java-Sort-Algorithms/CountingSort.java at master · mattryanmtl/Java-Sort-Algorithms · GitHub

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import java.util.Scanner;


/** Class CountingSort **/

public class CountingSort

{

    private static final int MAX_RANGE = 1000000;

    /** Counting Sort function **/

    public static void sort( int[] arr )

    {

        int N = arr.length;

        if (N == 0)

            return;

        /** find max and min values **/

        int max = arr[0], min = arr[0];

        for (int i = 1; i < N; i++)

        {

            if (arr[i] > max)

                max = arr[i];

            if (arr[i] < min)

                min = arr[i];

        }

        int range = max - min + 1;


        /** check if range is small enough for count array **/

        /** else it might give out of memory exception while allocating memory for array **/

        if (range > MAX_RANGE)

        {

            System.out.println("\nError : Range too large for sort");

            return;

        }


        int[] count = new int[range];

        /** make count/frequency array for each element **/

        for (int i = 0; i < N; i++)

            count[arr[i] - min]++;

        /** modify count so that positions in final array is obtained **/

        for (int i = 1; i < range; i++)

            count[i] += count[i - 1];

        /** modify original array **/

        int j = 0;

        for (int i = 0; i < range; i++)

            while (j < count[i])

                arr[j++] = i + min;

    }

    /** Main method **/

    public static void main(String[] args)

    {

        Scanner scan = new Scanner( System.in );

        System.out.println("Counting Sort Test\n");

        int n, i;

        /** Accept number of elements **/

        System.out.println("Enter number of integer elements");

        n = scan.nextInt();

        /** Create integer array on n elements **/

        int arr[] = new int[ n ];

        /** Accept elements **/

        System.out.println("\nEnter "+ n +" integer elements");

        for (i = 0; i < n; i++)

            arr[i] = scan.nextInt();

        /** Call method sort **/

        sort(arr);

        /** Print sorted Array **/

        System.out.println("\nElements after sorting ");

        for (i = 0; i < n; i++)

            System.out.print(arr[i]+" ");

        System.out.println();

    }

}