Merge pull request #41 from RaviTejaCMS/master

Added Merge Sort

Author: iam-abbas

SortingAlgos/C++/Merge Sort.cpp

@@ -0,0 +1,104 @@
+/* C program for Merge Sort */
+// https://www.geeksforgeeks.org/merge-sort/
+#include<stdlib.h> 
+#include<stdio.h> 
+
+// 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) 
+{ 
+	int i, j, k; 
+	int n1 = m - l + 1; 
+	int n2 = r - m; 
+
+	/* create temp arrays */
+	int L[n1], R[n2]; 
+
+	/* Copy data to temp arrays L[] and R[] */
+	for (i = 0; i < n1; i++) 
+		L[i] = arr[l + i]; 
+	for (j = 0; j < n2; j++) 
+		R[j] = arr[m + 1+ j]; 
+
+	/* Merge the temp arrays back into arr[l..r]*/
+	i = 0; // Initial index of first subarray 
+	j = 0; // Initial index of second subarray 
+	k = l; // Initial index of merged subarray 
+	while (i < n1 && j < n2) 
+	{ 
+		if (L[i] <= R[j]) 
+		{ 
+			arr[k] = L[i]; 
+			i++; 
+		} 
+		else
+		{ 
+			arr[k] = R[j]; 
+			j++; 
+		} 
+		k++; 
+	} 
+
+	/* Copy the remaining elements of L[], if there 
+	are any */
+	while (i < n1) 
+	{ 
+		arr[k] = L[i]; 
+		i++; 
+		k++; 
+	} 
+
+	/* Copy the remaining elements of R[], if there 
+	are any */
+	while (j < n2) 
+	{ 
+		arr[k] = R[j]; 
+		j++; 
+		k++; 
+	} 
+} 
+
+/* l is for left index and r is right index of the 
+sub-array of arr to be sorted */
+void mergeSort(int arr[], int l, int r) 
+{ 
+	if (l < r) 
+	{ 
+		// Same as (l+r)/2, but avoids overflow for 
+		// large l and h 
+		int m = l+(r-l)/2; 
+
+		// Sort first and second halves 
+		mergeSort(arr, l, m); 
+		mergeSort(arr, m+1, r); 
+
+		merge(arr, l, m, r); 
+	} 
+} 
+
+/* UTILITY FUNCTIONS */
+/* Function to print an array */
+void printArray(int A[], int size) 
+{ 
+	int i; 
+	for (i=0; i < size; i++) 
+		printf("%d ", A[i]); 
+	printf("\n"); 
+} 
+
+/* Driver program to test above functions */
+int main() 
+{ 
+	int arr[] = {12, 11, 13, 5, 6, 7}; 
+	int arr_size = sizeof(arr)/sizeof(arr[0]); 
+
+	printf("Given array is \n"); 
+	printArray(arr, arr_size); 
+
+	mergeSort(arr, 0, arr_size - 1); 
+
+	printf("\nSorted array is \n"); 
+	printArray(arr, arr_size); 
+	return 0; 
+}