quick sort_example

quickSort.java

public class quickSort {
    
    public static void main(String[] args) {
        int[] test = new int[]{5,1,1,2,0,0};        
        quickSortArr(test, 0, test.length-1);
        printArr(test);

    }

    public static void printArr(int[] arr) {
        System.out.println("test");
        for(int i = 0; i < arr.length; i++) {
            System.out.print(arr[i] + ", ");
        }
        System.out.println();
    }

    public static void quickSortArr(int[] arr, int l, int r) {
        if(l >= r) {
            return;
        }
        int begin = l, end = r;
        int pivot = arr[begin];
        while(begin < end) {
            while(begin < end && arr[end] >= pivot) { // !!! if use arr[end] > pivot the recycle would not end
                end--;
            } 
            if( begin < end) {
                arr[begin] = arr[end];
            }
            while(begin < end && arr[begin] <= pivot) {
                begin++;
            }
            if(begin < end) {
                arr[end] = arr[begin];
            }
        }
        arr[begin] = pivot;
        quickSortArr(arr, l, begin);
        quickSortArr(arr, begin+1, r);
        return;
    }
}