Merge Sort

Author: sathishmepco

InterviewPrograms/src/com/algorithm/sorting/MergeSort.java

@@ -0,0 +1,58 @@
+package com.algorithm.sorting;
+
+import java.util.Arrays;
+
+public class MergeSort {
+	public static void main(String[] args) {
+		int array[] = {90,23,101,45,65,23,67,89,34,23};
+		System.out.println("Before Sorting :: "+Arrays.toString(array));
+        sort(array,0,array.length-1);
+        System.out.println("After Sorting :: "+Arrays.toString(array));
+	}
+
+	public static void mergeSort(int array[], int leftIndex, int midIndex, int rightIndex) {
+		int n1 = midIndex - leftIndex + 1;
+		int n2 = rightIndex - midIndex;
+
+		int leftArray[] = new int[n1];
+		int rightArray[] = new int[n2];
+
+		for (int i = 0; i < n1; ++i)
+			leftArray[i] = array[leftIndex + i];
+		for (int j = 0; j < n2; ++j)
+			rightArray[j] = array[midIndex + 1 + j];
+
+		int i = 0, j = 0;
+		int k = leftIndex;
+		while (i < n1 && j < n2) {
+			if (leftArray[i] <= rightArray[j]) {
+				array[k] = leftArray[i];
+				i++;
+			} else {
+				array[k] = rightArray[j];
+				j++;
+			}
+			k++;
+		}
+
+		while (i < n1) {
+			array[k] = leftArray[i];
+			i++;
+			k++;
+		}
+		while (j < n2) {
+			array[k] = rightArray[j];
+			j++;
+			k++;
+		}
+	}
+
+	public static void sort(int array[], int leftIndex, int rightIndex) {
+		if (leftIndex < rightIndex) {
+			int midIndex = (leftIndex + rightIndex) / 2;
+			sort(array, leftIndex, midIndex);
+			sort(array, midIndex + 1, rightIndex);
+			mergeSort(array, leftIndex, midIndex, rightIndex);
+		}
+	}
+}