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- // Merge sort in C++
- #include <iostream>
- using namespace std;
- // 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;
- }
- // Driver program
- int main() {
- int arr[] = {6, 5, 12, 10, 9, 1};
- int size = sizeof(arr) / sizeof(arr[0]);
- mergeSort(arr, 0, size - 1);
- cout << "Sorted array: \n";
- printArray(arr, size);
- return 0;
- }
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