Class CountingSort

2_Basic Sorting/CountingSort.java:5–58

//Problem : Counting Sort

public class CountingSort {
    public static void countingSort(int arr[]) {
        int largest = Integer.MIN_VALUE;
        for(int i=0; i<arr.length; i++) {
            largest = Math.max(largest, arr[i]);
        }

        int count[] = new int[largest+1];
        for(int i=0; i<arr.length; i++) {
            count[arr[i]]++;
        }
        int j = 0;
        for(int i=0; i<count.length; i++) {
            while(count[i] > 0) {
                arr[j] = i;
                j++;
                count[i]--;
            }
        }
     }

     public static void countingSortDescending(int arr[]) {
        int largest = Integer.MIN_VALUE;
        for(int i=0; i<arr.length; i++) {
            largest = Math.max(largest, arr[i]);
        }

        int count[] = new int[largest+1];
        for(int i=0; i<arr.length; i++) {
            count[arr[i]]++;
        }
        int j = 0;
        for(int i=count.length-1; i>=0; i--) {
            while(count[i] > 0) {
                arr[j] = i;
                j++;
                count[i]--;
            }
        }
     }
 
     public static void printArr(int arr[]) {
         for(int i=0; i<arr.length; i++) {
             System.out.print(arr[i]+" ");
         }
         System.out.println();
     }
    
     public static void main(String args[]) {
         int arr[] = {1, 4, 1, 3, 2, 4, 3, 7};
         countingSortDescending(arr);
         printArr(arr);
     }
}