merge_sort.cpp: Add Cpp merge sort.

Cpp implementation of merge sort for NITSkmOS/Algorithms

closes NITSkmOS#258

README.md

@@ -16,7 +16,7 @@ This repository contains examples of various algorithms written on different pro
 | Algorithm                                                                                       | C                                     | CPP                                   | Java                                  | Python                                |
 |:----------------------------------------------------------------------------------------------- |:-------------------------------------:|:-------------------------------------:|:-------------------------------------:|:-------------------------------------:|
 | [Euclidean GCD](https://en.wikipedia.org/wiki/Euclidean_algorithm)                              | [:octocat:](euclidean_gcd/C)          |                                      | [:octocat:](euclidean_gcd/Java)        | [:octocat:](euclidean_gcd/Python)     |
-| [Merge Sort](https://en.wikipedia.org/wiki/Merge_sort)                                          | [:octocat:](merge_sort/C)             |                                       |[:octocat:](merge_sort/Java)                                       | [:octocat:](merge_sort/Python)        |
+| [Merge Sort](https://en.wikipedia.org/wiki/Merge_sort)                                          | [:octocat:](merge_sort/C)             | [:octocat:](merge_sort/Cpp)           |[:octocat:](merge_sort/Java)                                       | [:octocat:](merge_sort/Python)        |
 | [QuickSort](https://en.wikipedia.org/wiki/Quicksort)                                            | [:octocat:](quicksort/C)                                      |                                       |                                       | [:octocat:](quicksort/Python)         |
 | [Insertion Sort](https://en.wikipedia.org/wiki/Insertion_sort)                                  | [:octocat:](insertion_sort/C)         | [:octocat:](insertion_sort/Cpp)       |                                       | [:octocat:](insertion_sort/Python)    |
 | [Counting Sort](https://en.wikipedia.org/wiki/Counting_sort)                                    |[:octocat:](counting_sort/C)           | [:octocat:](counting_sort/Cpp)                                       |                                       | [:octocat:](counting_sort/Python)     |

merge_sort/Cpp/merge_sort.cpp

@@ -0,0 +1,72 @@
+#include <iostream>
+#include <cstdio>
+#include <vector>
+using namespace std;
+std::vector<int> vec;
+
+void join(std::vector<int>& arr, int, int, int);
+void sort(std::vector<int>& arr, int, int);
+void show(std::vector<int>& arr);
+
+int main() {
+	int n = 10, a, i, arr[] = {2, 4, 3, 6, 5, 1, 9, 0, 8, 7};
+	// scanf("%d", &n); //For custom input
+	// printf("Enter %ld number (space separated): ", n); //For custom inup
+	for (i = 0; i < n; i++) {
+		//scanf("%d", &a);
+		vec.push_back(arr[i]); //vec.push_back(a); // For custom input
+	}
+	a = 0;
+	sort(vec, a, n-1);
+	show(vec);
+	return 0;
+}
+
+void join(std::vector<int>& arr, int l, int m, int r) {
+	// Merge operation of merge sort.
+	int i, j, k;
+	int s1 = m-l+1, s2 = r-m;
+	int L[s1], R[s2];
+	for (i = 0; i < s1; i++)
+		L[i] = arr[l+i];
+	for (j = 0; j < s2; j++)
+		R[j] = arr[m+j+1];
+	i = 0; j = 0; k = l;
+	while (i < s1 && j < s2) {
+		if (L[i] < R[j]) {
+			arr[k] = L[i];
+			i++;
+		} else {
+			arr[k] = R[j];
+			j++;
+		}
+		k++;
+	}
+	while (i < s1) {
+		arr[k] = L[i]; i++; k++;
+	}
+	while (j < s2) {
+		arr[k] = R[j]; j++; k++;
+	}
+}
+
+void sort(std::vector<int>& arr, int l, int r) {
+	// The major implementation of merge sort algorithm
+	if (l < r) {
+		int m = l+(r-l)/2;
+		sort(arr, l, m);
+		sort(arr, m+1, r);
+		join(arr, l, m, r);
+	}
+}
+
+void show(std::vector<int>& arr) {
+	// A basic function to view vector values
+	cout << "Sorted element using Merge Sort: ";
+	std::vector<int>::iterator v = arr.begin();
+	while (v != arr.end()) {
+		cout << *v <<" ";
+		v++;
+	}
+	cout << endl;
+}