CountingSort.java Added java implementation of counting sort.

counting_sort/Java/CountingSort.java

@@ -0,0 +1,47 @@
+/*Counting Sort algorithm- In Counting sort, the frequencies of distinct elements of the array 
+to be sorted is counted and stored in an auxiliary array, by mapping its value as an index of
+the auxiliary array.
+Time Complexity- The below algorithm takes time O(n+m)
+where n= number of elements in the array to be sorted, and
+m= size of the auxilliary array
+
+This is a linear time algorithm and can be used when a small nember of elements needs to be sorted.
+*/
+public class CountingSort {
+    static int[] countingSort(int[] array){
+        //find the maximum element from the array
+        int max = array[0];
+        for (int i = 1; i < array.length;i++){
+            if(array[i]>max){
+                max= array[i];
+            }
+        }
+        //declare an auxillary array
+        int[] auxArray= new int[max+1];
+        for(int i=0;i<array.length;i++){
+            auxArray[array[i]]++;
+        }
+        //declare an sorted array of the same length
+        int[] sortedAux= new int[array.length];
+        int temp=0;
+        int j=0;
+        for(int i=0;i<max+1;i++){
+            temp= auxArray[i];
+            while(temp>0){
+                sortedAux[j]=i;
+                j++;
+                temp--;
+            }
+        }
+        return sortedAux;
+    }
+    public static void main(String[] args) {
+        int[] array = {5,2,9,5,2,3,5};
+        int[] sortedAux= countingSort(array);
+        //printing the sorted array
+        for(int i=0;i<sortedAux.length;i++){
+            System.out.print(sortedAux[i]+" ");
+        }
+    }
+
+}