# Merge Sort in C++ ```A simple program to demonstrate merge sort algorithm in C++ programming language.

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``````#include <iostream>
#include <vector>

// Merge two sorted arrays into one sorted array
void merge(std::vector<int>& arr, int left, int mid, int right) {
int n1 = mid - left + 1;
int n2 = right - mid;

std::vector<int> L(n1);
std::vector<int> R(n2);

// Copy data to temporary arrays L and R
for (int i = 0; i < n1; ++i)
L[i] = arr[left + i];
for (int j = 0; j < n2; ++j)
R[j] = arr[mid + 1 + j];

int i = 0, j = 0, k = left;

// Merge the temporary arrays back into arr
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 and R (if any)
while (i < n1) {
arr[k] = L[i];
++i;
++k;
}

while (j < n2) {
arr[k] = R[j];
++j;
++k;
}
}

// Merge Sort function
void mergeSort(std::vector<int>& arr, int left, int right) {
if (left < right) {
int mid = left + (right - left) / 2;

// Sort the first and second halves
mergeSort(arr, left, mid);
mergeSort(arr, mid + 1, right);

// Merge the sorted halves
merge(arr, left, mid, right);
}
}

int main() {
std::vector <int> arr = {12, 11, 13,-67,23,-452, 5, 6, 7};

std::cout << "\n\t\tMerge Sort in C++\n\n";
std::cout << "\n\tOriginal array: ";
for (int num : arr)
std::cout << num << " ";

mergeSort(arr, 0, arr.size() - 1);

std::cout << "\n\n\tSorted array: ";
for (int num : arr)
std::cout << num << " ";
std::cout <<"\n\n";
return 0;
}
``````