Merge pull request #333 from vijaykrishna-11/Added-CountingSort

Added Counting Sort Algorithm

Author: kelvins

README.md

@@ -2923,8 +2923,8 @@ In order to achieve greater coverage and encourage more people to contribute to
                 </a>
             </td>
             <td> <!-- Java -->
-                <a href="./CONTRIBUTING.md">
-                    <img align="center" height="25" src="./logos/github.svg" />
+                <a href="./src/java/CountingSort.java">
+                    <img align="center" height="25" src="./logos/java.svg" />
                 </a>
             </td>
             <td> <!-- Python -->

src/java/CountingSort.java

@@ -0,0 +1,54 @@
+public class CountingSort {
+
+  int getMax(int[] a, int n) {
+    int max = a[0];
+    for (int i = 1; i < n; i++) {
+      if (a[i] > max) max = a[i];
+    }
+    return max;
+  }
+
+  void countSort(int[] a, int n) {
+    int[] output = new int[n + 1];
+    int max = getMax(a, n);
+    // int max = 42;
+    int[] count = new int[max + 1];
+
+    for (int i = 0; i <= max; ++i) {
+      count[i] = 0;
+    }
+
+    for (int i = 0; i < n; i++) {
+      count[a[i]]++;
+    }
+
+    for (int i = 1; i <= max; i++) count[i] += count[i - 1];
+
+    for (int i = n - 1; i >= 0; i--) {
+      output[count[a[i]] - 1] = a[i];
+      count[a[i]]--;
+    }
+
+    for (int i = 0; i < n; i++) {
+      a[i] = output[i];
+    }
+  }
+
+  /* Function to print the array elements */
+  void printArray(int a[], int n) {
+    int i;
+    for (i = 0; i < n; i++) System.out.print(a[i] + " ");
+  }
+
+  public static void main(String args[]) {
+    int a[] = {11, 30, 24, 7, 31, 16, 39, 41};
+    int n = a.length;
+    CountingSort c1 = new CountingSort();
+    System.out.println("\nBefore sorting array elements are - ");
+    c1.printArray(a, n);
+    c1.countSort(a, n);
+    System.out.println("\nAfter sorting array elements are - ");
+    c1.printArray(a, n);
+    System.out.println();
+  }
+}