Create mergesort.java

mergesort.java

@@ -0,0 +1,83 @@
+
+class MergeSort 
+{ 
+
+	void merge(int arr[], int l, int m, int r) 
+	{ 
+		int n1 = m - l + 1; 
+		int n2 = r - m; 
+		int L[] = new int [n1]; 
+		int R[] = new int [n2]; 
+
+		for (int i=0; i<n1; ++i) 
+			L[i] = arr[l + i]; 
+		for (int j=0; j<n2; ++j) 
+			R[j] = arr[m + 1+ j]; 
+
+		int i = 0, j = 0; 
+
+		int k = l; 
+		while (i < n1 && j < n2) 
+		{ 
+			if (L[i] <= R[j]) 
+			{ 
+				arr[k] = L[i]; 
+				i++; 
+			} 
+			else
+			{ 
+				arr[k] = R[j]; 
+				j++; 
+			} 
+			k++; 
+		} 
+
+		while (i < n1) 
+		{ 
+			arr[k] = L[i]; 
+			i++; 
+			k++; 
+		} 
+		while (j < n2) 
+		{ 
+			arr[k] = R[j]; 
+			j++; 
+			k++; 
+		} 
+	} 
+
+
+	void sort(int arr[], int l, int r) 
+	{ 
+		if (l < r) 
+		{ 
+			int m = (l+r)/2; 
+
+			sort(arr, l, m); 
+			sort(arr , m+1, r); 
+
+			merge(arr, l, m, r); 
+		} 
+	}
+
+	static void printArray(int arr[]) 
+	{ 
+		int n = arr.length; 
+		for (int i=0; i<n; ++i) 
+			System.out.print(arr[i] + " "); 
+		System.out.println(); 
+	}
+	public static void main(String args[]) 
+	{ 
+		int arr[] = {12, 11, 13, 5, 6, 7}; 
+
+		System.out.println("Given Array"); 
+		printArray(arr); 
+
+		MergeSort ob = new MergeSort(); 
+		ob.sort(arr, 0, arr.length-1); 
+
+		System.out.println("\nSorted array"); 
+		printArray(arr); 
+	} 
+}