quick sort

quick.cpp

#include <iostream>
#include <algorithm>
#include <vector>
#include <stdlib.h>
#include <time.h>
#include <map>

#define MAX 20
using namespace std;

void quickSort(int arr[], int left, int right) {
	int i = left, j = right;
	int tmp;
	int pivot = arr[(left + right) / 2];

	// partition
	while (i <= j) {
		while (arr[i] < pivot)
			i++;
        while (pivot < arr[j])
			j--;
        if (i <= j) {
			tmp = arr[i];
			arr[i] = arr[j];
			arr[j] = tmp;
			i++;
			j--;
        }
	};

	// recursion
	if (left < j)
		quickSort(arr, left, j);
	if (i < right)
		quickSort(arr, i, right);
}

void printArray(int arr[], int length) {
	for(int i = 0; i < length; i++){
		cout<< arr[i] << " ";
	}
	cout<< endl;
}

int main() {
	// init
	int arr[MAX];
	srand(time(NULL));
	for(int i = 0; i < MAX; i++){
		arr[i] = rand() % 20 + 1;
	}

	cout<<"before quickSorting: ";
	printArray(arr, MAX);

	quickSort(arr, 0, MAX-1);

	cout<<"after quickSorting: ";
	printArray(arr, MAX);

	return 0;
}