p22MergeSort.cpp

// 22.Write a program to sort list using merge sort. 
#include <iostream>
using namespace std;

// Merge two subarrays of arr[]
void merge(int arr[], int left, int mid, int right) {
    int n1 = mid - left + 1;
    int n2 = right - mid;

    // Create temporary arrays
    int L[n1], R[n2];

    // Copy data to temporary arrays
    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];

    // Merge the temp arrays back into arr[]
    int i = 0, j = 0, k = left;

    while (i < n1 && j < n2) {
        if (L[i] <= R[j]) {
            arr[k] = L[i];
            i++;
        } else {
            arr[k] = R[j];
            j++;
        }
        k++;
    }

    // Copy any remaining elements of L[]
    while (i < n1) {
        arr[k] = L[i];
        i++;
        k++;
    }

    // Copy any remaining elements of R[]
    while (j < n2) {
        arr[k] = R[j];
        j++;
        k++;
    }
}

// Merge Sort function
void mergeSort(int arr[], int left, int right) {
    if (left < right) {
        int mid = left + (right - left) / 2;

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

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

// Print array
void printArray(int arr[], int size) {
    cout << "Sorted array: ";
    for (int i = 0; i < size; i++)
        cout << arr[i] << " ";
    cout << endl;
}

// Main function
int main() {
    int arr[] = {38, 27, 43, 3, 9, 82, 10};
    int size = sizeof(arr) / sizeof(arr[0]);

    mergeSort(arr, 0, size - 1);

    printArray(arr, size);

    cout << "\nProgram by ABHISHEK SINGH" << endl;
    cout << "Roll No: 2315272/2435222" << endl;

    return 0;
}