merge_sort.cpp

#include <iostream>
#include <vector>
using namespace std;

void merge(vector<int> &arr, int low, int mid, int high)
{
    vector<int> temp;

    // starting index of left and right part
    int left = low;
    int right = mid + 1;

    // comparing elements from both parts and adding smaller one
    while (left <= mid && right <= high)
    {
        if (arr[left] <= arr[right])
        {
            temp.push_back(arr[left]);
            left++;
        }
        else
        {
            temp.push_back(arr[right]);
            right++;
        }
    }

    // if any elements are left in the left part
    while (left <= mid)
    {
        temp.push_back(arr[left]);
        left++;
    }

    // if any elements are left in the right part
    while (right <= high)
    {
        temp.push_back(arr[right]);
        right++;
    }

    // putting the sorted elements back in the original array
    for (int i = low; i <= high; i++)
    {
        arr[i] = temp[i - low];
    }
}

void ms(vector<int> &arr, int low, int high)
{
    // stop when only one element is left
    if (low == high)
        return;
    int mid = (low + high) / 2;

    // divide the array into two parts
    ms(arr, low, mid);
    ms(arr, mid + 1, high);

    // merge both sorted parts
    merge(arr, low, mid, high);
}

int main()
{
    vector<int> mergi = {5, 3, 4, 1, 2};
    int n = mergi.size();

    // sorting the complete array
    ms(mergi, 0, n - 1);

    // printing the sorted array
    for (int i = 0; i < n; i++)
    {
        cout << mergi[i] << " ";
    }
    return 0;
}