Add merge sort

bubblesort.java

@@ -0,0 +1,57 @@
+// Optimized java implementation 
+// of Bubble sort 
+import java.io.*; 
+
+class GFG 
+{ 
+	// An optimized version of Bubble Sort 
+	static void bubbleSort(int arr[], int n) 
+	{ 
+		int i, j, temp; 
+		boolean swapped; 
+		for (i = 0; i < n - 1; i++) 
+		{ 
+			swapped = false; 
+			for (j = 0; j < n - i - 1; j++) 
+			{ 
+				if (arr[j] > arr[j + 1]) 
+				{ 
+					// swap arr[j] and arr[j+1] 
+					temp = arr[j]; 
+					arr[j] = arr[j + 1]; 
+					arr[j + 1] = temp; 
+					swapped = true; 
+				} 
+			} 
+
+			// IF no two elements were 
+			// swapped by inner loop, then break 
+			if (swapped == false) 
+				break; 
+		} 
+	} 
+
+	// Function to print an array 
+	static void printArray(int arr[], int size) 
+	{ 
+		int i; 
+		for (i = 0; i < size; i++) 
+			System.out.print(arr[i] + " "); 
+		System.out.println(); 
+	} 
+
+	// Driver program 
+	public static void main(String args[]) 
+	{ 
+		int arr[] = { 64, 34, 25, 12, 22, 11, 90 }; 
+		int n = arr.length; 
+		bubbleSort(arr, n); 
+		System.out.println("Sorted array: "); 
+		printArray(arr, n); 
+	} 
+} 
+
+
+// This code is contributed 
+// by Nikita Tiwari. 
+

insertionsort.java

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+// Java program for implementation of Insertion Sort 
+class InsertionSort { 
+	/*Function to sort array using insertion sort*/
+	void sort(int arr[]) 
+	{ 
+		int n = arr.length; 
+		for (int i = 1; i < n; ++i) { 
+			int key = arr[i]; 
+			int j = i - 1; 
+
+			/* Move elements of arr[0..i-1], that are 
+			greater than key, to one position ahead 
+			of their current position */
+			while (j >= 0 && arr[j] > key) { 
+				arr[j + 1] = arr[j]; 
+				j = j - 1; 
+			} 
+			arr[j + 1] = key; 
+		} 
+	} 
+
+	/* A utility function to print array of size n*/
+	static void printArray(int arr[]) 
+	{ 
+		int n = arr.length; 
+		for (int i = 0; i < n; ++i) 
+			System.out.print(arr[i] + " "); 
+
+		System.out.println(); 
+	} 
+
+	// Driver method 
+	public static void main(String args[]) 
+	{ 
+		int arr[] = { 12, 11, 13, 5, 6 }; 
+
+		InsertionSort ob = new InsertionSort(); 
+		ob.sort(arr); 
+
+		printArray(arr); 
+	} 
+} /* This code is contributed by Rajat Mishra. */
+

mergesort.java

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+/* Java program for Merge Sort */
+class MergeSort 
+{ 
+	// Merges two subarrays of arr[]. 
+	// First subarray is arr[l..m] 
+	// Second subarray is arr[m+1..r] 
+	void merge(int arr[], int l, int m, int r) 
+	{ 
+		// Find sizes of two subarrays to be merged 
+		int n1 = m - l + 1; 
+		int n2 = r - m; 
+
+		/* Create temp arrays */
+		int L[] = new int [n1]; 
+		int R[] = new int [n2]; 
+
+		/*Copy data to temp arrays*/
+		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]; 
+
+
+		/* Merge the temp arrays */
+
+		// Initial indexes of first and second subarrays 
+		int i = 0, j = 0; 
+
+		// Initial index of merged subarry array 
+		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++; 
+		} 
+
+		/* Copy remaining elements of L[] if any */
+		while (i < n1) 
+		{ 
+			arr[k] = L[i]; 
+			i++; 
+			k++; 
+		} 
+
+		/* Copy remaining elements of R[] if any */
+		while (j < n2) 
+		{ 
+			arr[k] = R[j]; 
+			j++; 
+			k++; 
+		} 
+	} 
+
+	// Main function that sorts arr[l..r] using 
+	// merge() 
+	void sort(int arr[], int l, int r) 
+	{ 
+		if (l < r) 
+		{ 
+			// Find the middle point 
+			int m = (l+r)/2; 
+
+			// Sort first and second halves 
+			sort(arr, l, m); 
+			sort(arr , m+1, r); 
+
+			// Merge the sorted halves 
+			merge(arr, l, m, r); 
+		} 
+	} 
+
+	/* A utility function to print array of size n */
+	static void printArray(int arr[]) 
+	{ 
+		int n = arr.length; 
+		for (int i=0; i<n; ++i) 
+			System.out.print(arr[i] + " "); 
+		System.out.println(); 
+	} 
+
+	// Driver method 
+	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); 
+	} 
+} 
+/* This code is contributed by Rajat Mishra */
+

selectionSort.java

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+// Java program for implementation of Selection Sort 
+class SelectionSort 
+{ 
+	void sort(int arr[]) 
+	{ 
+		int n = arr.length; 
+
+		// One by one move boundary of unsorted subarray 
+		for (int i = 0; i < n-1; i++) 
+		{ 
+			// Find the minimum element in unsorted array 
+			int min_idx = i; 
+			for (int j = i+1; j < n; j++) 
+				if (arr[j] < arr[min_idx]) 
+					min_idx = j; 
+
+			// Swap the found minimum element with the first 
+			// element 
+			int temp = arr[min_idx]; 
+			arr[min_idx] = arr[i]; 
+			arr[i] = temp; 
+		} 
+	} 
+
+	// Prints the array 
+	void printArray(int arr[]) 
+	{ 
+		int n = arr.length; 
+		for (int i=0; i<n; ++i) 
+			System.out.print(arr[i]+" "); 
+		System.out.println(); 
+	} 
+
+	// Driver code to test above 
+	public static void main(String args[]) 
+	{ 
+		SelectionSort ob = new SelectionSort(); 
+		int arr[] = {64,25,12,22,11}; 
+		ob.sort(arr); 
+		System.out.println("Sorted array"); 
+		ob.printArray(arr); 
+	} 
+} 
+/* This code is contributed by Rajat Mishra*/
+