mergesort.cpp

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

// Class for Merge Sort
class MergeSort {
public:
    // Function to merge two sorted subarrays into one sorted array
    void merge(vector<int>& arr, int left, int mid, int right) {
        int n1 = mid - left + 1;  // Size of the left subarray
        int n2 = right - mid;     // Size of the right subarray

        // Temporary arrays for the left and right subarrays
        vector<int> leftArr(n1), rightArr(n2);

        // Copy data into temporary arrays
        for (int i = 0; i < n1; i++) {
            leftArr[i] = arr[left + i];
        }
        for (int i = 0; i < n2; i++) {
            rightArr[i] = arr[mid + 1 + i];
        }

        // Merge the two subarrays back into the original array
        int i = 0, j = 0, k = left;
        while (i < n1 && j < n2) {
            if (leftArr[i] <= rightArr[j]) {
                arr[k++] = leftArr[i++];
            } else {
                arr[k++] = rightArr[j++];
            }
        }

        // Copy remaining elements from leftArr, if any
        while (i < n1) {
            arr[k++] = leftArr[i++];
        }

        // Copy remaining elements from rightArr, if any
        while (j < n2) {
            arr[k++] = rightArr[j++];
        }
    }

    // Merge sort function to recursively divide the array
    void mergeSort(vector<int>& arr, int left, int right) {
        if (left < right) {
            int mid = left + (right - left) / 2;

            // Recursively sort the two halves
            mergeSort(arr, left, mid);
            mergeSort(arr, mid + 1, right);

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

    // Function to print the array
    void printArray(const vector<int>& arr) {
        for (int num : arr) {
            cout << num << " ";
        }
        cout << endl;
    }
};

int main() {
    int n;

    // Input the size of the array
    cout << "Enter the size of the array: ";
    cin >> n;

    // Input array elements
    vector<int> arr(n);
    cout << "Enter " << n << " elements: ";
    for (int i = 0; i < n; i++) {
        cin >> arr[i];
    }

    // Create an object of the MergeSort class
    MergeSort ms;

    // Perform merge sort
    ms.mergeSort(arr, 0, n - 1);

    // Print the sorted array
    cout << "Sorted array: ";
    ms.printArray(arr);

    return 0;
}