diff --git a/Merge_sort b/Merge_sort new file mode 100644 index 0000000..344e9d4 --- /dev/null +++ b/Merge_sort @@ -0,0 +1,106 @@ +// C++ program for Merge Sort +#include +using namespace std; + +// Merges two subarrays of array[]. +// First subarray is arr[begin..mid] +// Second subarray is arr[mid+1..end] +void merge(int array[], int const left, int const mid, + int const right) +{ + auto const subArrayOne = mid - left + 1; + auto const subArrayTwo = right - mid; + + // Create temp arrays + auto *leftArray = new int[subArrayOne], + *rightArray = new int[subArrayTwo]; + + // Copy data to temp arrays leftArray[] and rightArray[] + for (auto i = 0; i < subArrayOne; i++) + leftArray[i] = array[left + i]; + for (auto j = 0; j < subArrayTwo; j++) + rightArray[j] = array[mid + 1 + j]; + + auto indexOfSubArrayOne + = 0, // Initial index of first sub-array + indexOfSubArrayTwo + = 0; // Initial index of second sub-array + int indexOfMergedArray + = left; // Initial index of merged array + + // Merge the temp arrays back into array[left..right] + while (indexOfSubArrayOne < subArrayOne + && indexOfSubArrayTwo < subArrayTwo) { + if (leftArray[indexOfSubArrayOne] + <= rightArray[indexOfSubArrayTwo]) { + array[indexOfMergedArray] + = leftArray[indexOfSubArrayOne]; + indexOfSubArrayOne++; + } + else { + array[indexOfMergedArray] + = rightArray[indexOfSubArrayTwo]; + indexOfSubArrayTwo++; + } + indexOfMergedArray++; + } + // Copy the remaining elements of + // left[], if there are any + while (indexOfSubArrayOne < subArrayOne) { + array[indexOfMergedArray] + = leftArray[indexOfSubArrayOne]; + indexOfSubArrayOne++; + indexOfMergedArray++; + } + // Copy the remaining elements of + // right[], if there are any + while (indexOfSubArrayTwo < subArrayTwo) { + array[indexOfMergedArray] + = rightArray[indexOfSubArrayTwo]; + indexOfSubArrayTwo++; + indexOfMergedArray++; + } + delete[] leftArray; + delete[] rightArray; +} + +// begin is for left index and end is +// right index of the sub-array +// of arr to be sorted */ +void mergeSort(int array[], int const begin, int const end) +{ + if (begin >= end) + return; // Returns recursively + + auto mid = begin + (end - begin) / 2; + mergeSort(array, begin, mid); + mergeSort(array, mid + 1, end); + merge(array, begin, mid, end); +} + +// UTILITY FUNCTIONS +// Function to print an array +void printArray(int A[], int size) +{ + for (auto i = 0; i < size; i++) + cout << A[i] << " "; +} + +// Driver code +int main() +{ + int arr[] = { 12, 11, 13, 5, 6, 7 }; + auto arr_size = sizeof(arr) / sizeof(arr[0]); + + cout << "Given array is \n"; + printArray(arr, arr_size); + + mergeSort(arr, 0, arr_size - 1); + + cout << "\nSorted array is \n"; + printArray(arr, arr_size); + return 0; +} + +// This code is contributed by Mayank Tyagi +// This code was revised by Joshua Estes