Merge pull request larissalages#15 from adenashameem/master

 Added Merge Sort in Java

Author: larissalages

classical_algorithms/MergeSort.java

@@ -0,0 +1,111 @@
+import java.util.*;
+import java.lang.*;
+
+
+class MergeSort
+{
+
+	public void sort(int a[], int low, int high)
+	{
+		if(low<high)
+		{
+			int mid=(low+high)/2;
+			sort(a,low,mid);
+			sort(a,mid+1,high);
+			merge(a,low,mid,high);
+		}
+	}
+
+	public void merge(int a[], int low, int mid, int high)
+	{
+		int h=low, i=low, j=mid+1,k;
+		int b[]=new int[high+1];
+
+		while((h<=mid) && (j<=high))
+		{
+			if(a[h]<a[j])
+			{
+				b[i]=a[h];
+				h=h+1;
+			}
+			else
+			{
+				b[i]=a[j];
+				j=j+1;
+			}
+		i=i+1;
+		}
+
+
+		if(h>mid)
+		{
+			for(k=j;k<=high;k++)
+			{
+				b[i]=a[k];
+				i=i+1;
+			}
+		}
+
+
+		if(j>high)
+		{
+			for(k=h;k<=mid;k++)
+			{
+				b[i]=a[k];
+				i=i+1;
+			}
+		}
+
+		for(k=low;k<=high;k++)
+		{
+			a[k]=b[k];
+		}
+	}
+
+   	static void printArray(int a[], int n)
+	{
+	
+		for(int i=0;i<n;i++)
+		{
+			System.out.print( a[i]+ "\t");
+		}
+	}
+
+ 	public static void main(String args[])
+	{
+		try{
+			int low,high,mid;
+			int n,i;
+
+			Scanner scan= new Scanner(System.in);
+	
+			System.out.println("How many elements do you want in the array?");
+			n=scan.nextInt();
+			int a[]= new int[n];
+			System.out.println("Enter the array elements one by one");
+			for(i=0;i<n;i++)
+			{
+				a[i]=scan.nextInt();		
+			}
+
+			System.out.println("Array before sorting is:");
+			printArray(a, n);
+			low=0;
+			high=n-1;
+
+  			MergeSort obj = new MergeSort(); 
+      			obj.sort(a, low, high);
+                  			System.out.println();
+
+			System.out.println("The sorted array is: ");
+			printArray(a, n);
+
+		}catch(Exception e){e.printStackTrace();}
+                   
+	}
+}
+
+
+
+
+