Create quicksort.cpp

Author: kanishka-28

CPP/sorting/quicksort.cpp

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+/* C++ implementation of QuickSort */
+#include <bits/stdc++.h>
+using namespace std;
+
+// A utility function to swap two elements
+void swap(int* a, int* b)
+{
+	int t = *a;
+	*a = *b;
+	*b = t;
+}
+
+/* This function takes last element as pivot, places
+the pivot element at its correct position in sorted
+array, and places all smaller (smaller than pivot)
+to left of pivot and all greater elements to right
+of pivot */
+int partition(int arr[], int low, int high)
+{
+	int pivot = arr[high]; // pivot
+	int i
+		= (low
+		- 1); // Index of smaller element and indicates
+				// the right position of pivot found so far
+
+	for (int j = low; j <= high - 1; j++) {
+		// If current element is smaller than the pivot
+		if (arr[j] < pivot) {
+			i++; // increment index of smaller element
+			swap(&arr[i], &arr[j]);
+		}
+	}
+	swap(&arr[i + 1], &arr[high]);
+	return (i + 1);
+}
+
+/* The main function that implements QuickSort
+arr[] --> Array to be sorted,
+low --> Starting index,
+high --> Ending index */
+void quickSort(int arr[], int low, int high)
+{
+	if (low < high) {
+		/* pi is partitioning index, arr[p] is now
+		at right place */
+		int pi = partition(arr, low, high);
+
+		// Separately sort elements before
+		// partition and after partition
+		quickSort(arr, low, pi - 1);
+		quickSort(arr, pi + 1, high);
+	}
+}
+
+/* Function to print an array */
+void printArray(int arr[], int size)
+{
+	int i;
+	for (i = 0; i < size; i++)
+		cout << arr[i] << " ";
+	cout << endl;
+}
+
+// Driver Code
+int main()
+{
+	int arr[] = { 10, 7, 8, 9, 1, 5 };
+	int n = sizeof(arr) / sizeof(arr[0]);
+	quickSort(arr, 0, n - 1);
+	cout << "Sorted array: \n";
+	printArray(arr, n);
+	return 0;
+}