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/***************************************************************
* Name: Rafael Orta
* Course: Computer Science & Programming
* Class: PDS04225
* Assignment Date: 04/17/22
* File Name: Merge-Sort.cpp
*****************************************************************
* Purpose: Demonstrate the implementation of Merge-Sort using C++
*****************************************************************/
#include <iostream>
using namespace std;
// Merge two subarrays L and M into arr
void merge(int[], int, int, int);
// Divide the array into two subarrays, sort them and merge them
void mergeSort(int[], int, int);
// Print the array
void printArray(int[], int);
// Driver program
int main() {
int arr[] = {6, 5, 12, 10, 9, 1};
cout << "Unsorted array:" << endl;
printArray(arr, 6);
int size = sizeof(arr) / sizeof(arr[0]);
mergeSort(arr, 0, size - 1);
cout << "Sorted array: \n";
printArray(arr, size);
return 0;
}
// Merge two subarrays L and M into arr
void merge(int arr[], int p, int q, int r) {
// Create L ← A[p..q] and M ← A[q+1..r]
int n1 = q - p + 1;
int n2 = r - q;
int L[n1], M[n2];
for (int i = 0; i < n1; i++)
L[i] = arr[p + i];
for (int j = 0; j < n2; j++)
M[j] = arr[q + 1 + j];
// Maintain current index of sub-arrays and main array
int i, j, k;
i = 0;
j = 0;
k = p;
// Until we reach either end of either L or M, pick larger among
// elements L and M and place them in the correct position at A[p..r]
while (i < n1 && j < n2) {
if (L[i] <= M[j]) {
arr[k] = L[i];
i++;
} else {
arr[k] = M[j];
j++;
}
k++;
}
// When we run out of elements in either L or M,
// pick up the remaining elements and put in A[p..r]
while (i < n1) {
arr[k] = L[i];
i++;
k++;
}
while (j < n2) {
arr[k] = M[j];
j++;
k++;
}
}
// Divide the array into two subarrays, sort them and merge them
void mergeSort(int arr[], int l, int r) {
if (l < r) {
// m is the point where the array is divided into two subarrays
int m = l + (r - l) / 2;
mergeSort(arr, l, m);
mergeSort(arr, m + 1, r);
// Merge the sorted subarrays
merge(arr, l, m, r);
}
}
// Print the array
void printArray(int arr[], int size) {
for (int i = 0; i < size; i++)
cout << arr[i] << " ";
cout << endl;
}
Compiling Program...
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