package sort;

public class QuickSort {

	public static void main(String[] args) {
		int[] unsortedArray = new int[]{6, 5, 3, 1, 8, 7, 2, 4};
		quickSort(unsortedArray);
		System.out.println("After sort: ");
		for (int item : unsortedArray) {
			System.out.print(item + " ");
		}
	}
	
	public static void quickSort2(int[] array, int l, int u) {
		for (int item : array) {
			System.out.print(item + " ");
		}
		System.out.println();
		
		if (l >= u) return ;
		int pivot = array[l] ;    // 定义一个基准，最左侧的值
		int left = l + 1 ;
		int right = u ;
		while (left <= right) {
			// 左侧内循环自增 i, 直到遇到不小于基准元素的值为止。
			while (left <= right && array[left] < pivot) {
				left++ ;
			}
			// 右侧内循环自减 j, 直到遇到小于基准元素的值为止。
			while (left <= right && array[right] >= pivot) {
				right-- ;
			}
			if (left > right) break ;
			// swap array[left] with array[right] while left <= right
			int temp = array[left] ;
			array[left] = array[right] ;
			array[right] = temp ;
		}
		/* swap the smaller with pivot */
		/**
		 * （6,5,3,1,4,2,7,8）
		 * 之后进行6和2的交换位置操作
		 * （2,5,3,1,4,6,7,8）
		 * 重复进行以上操作
		 */
		int temp = array[right] ;
		array[right] = array[l] ;	
		array[l] = temp ;   
//		System.out.println(l + " " + right + " " + u);   // 0 5 7
		quickSort2(array, l, right-1);
		quickSort2(array, right+1, u);
	}

	public static void quickSort(int[] array) {
		quickSort2(array, 0, array.length-1);		
	}
}

public class Sort {
    public static void main(String[] args) {
        int unsortedArray[] = new int[]{6, 5, 3, 1, 8, 7, 2, 4};
        quickSort(unsortedArray);
        System.out.println("After sort: ");
        for (int item : unsortedArray) {
            System.out.print(item + " ");
        }
    }

    public static void quickSort1(int[] array, int l, int u) {
        for (int item : array) {
            System.out.print(item + " ");
        }
        System.out.println();

        if (l >= u) return;
        int m = l;
        for (int i = l + 1; i <= u; i++) {
            if (array[i] < array[l]) {
                m += 1;
                int temp = array[m];
                array[m] = array[i];
                array[i] = temp;
            }
        }
        // swap between array[m] and array[l]
        // put pivot in the mid
        int temp = array[m];
        array[m] = array[l];
        array[l] = temp;

        quickSort1(array, l, m - 1);
        quickSort1(array, m + 1, u);
    }

    public static void quickSort(int[] array) {
        quickSort1(array, 0, array.length - 1);
    }
}

package myTest;

public class ArrayIns
{
	private long[] theArray ; 		// def to array to theArray
	private int nElems ; 			// number of data items 

	public ArrayIns(int max){ 		// constructor
		theArray = new long[max] ;  // create the array
		nElems = 0 ;  				// no item yet
 	}
	
	public void insert(long value){	// put element into array
		theArray[nElems] = value ;	// insert it
		nElems++ ;		 			// increment size
	}
	
	public void display(){			// display array contents
		System.out.print("A=");
		for (int i = 0; i < nElems; i++) {			// for each element
			System.out.print(theArray[i] + " ");	// display
		}
		System.out.println("");
	}
	
	public void quickSort(){
		recQuickSort(0, nElems-1);
	}
	
	public void recQuickSort(int left, int right){
		if (right-left <= 0) {		// if size<=1 
			return ;				// already sorted
		}
		else{						
			long pivot = theArray[right] ;		//rightmost item
			
			int partition = partitionIt(left,right,pivot) ; // partition range
			recQuickSort(left, partition-1);	// sort left side
			recQuickSort(partition+1, right);	// sort right side
		}
	}

	private int partitionIt(int left, int right, long pivot) {
		int leftPtr = left-1 ; 		// left	(after ++)
		int rightPtr = right ;		// right-1 (after--)
		while (true) 
		{							// find bigger item
			while (theArray[++leftPtr] < pivot) 
				;
									// find smaller item
			while (rightPtr > 0 && theArray[--rightPtr] > pivot) 
				;
			
			if (leftPtr >= rightPtr) {			// if pointers cross 
				break ;							// partition done 
			}
			else{								// not crossed so
				swap(leftPtr,rightPtr) ;		// swap elements 
			}			
		}
		swap(leftPtr,right) ;				// restore pivot
		return leftPtr ;						// return pivot location
	}

	private void swap(int dex1, int dex2) {	// swap two elements
		long temp = theArray[dex1] ;		// A into temp 
		theArray[dex1] = theArray[dex2] ;	// B into A
		theArray[dex2] = temp ;				// temp into B 
	}	
}

package myTest;

public class QuickSort1 
{
	public static void main(String[] args) {
		int maxSize = 18 ;		// array size
		ArrayIns arr ;
		arr = new ArrayIns(maxSize) ;	// create array 
		
		for (int i = 0; i < maxSize; i++) {	// fill array with random numbers
			long n = (int)(java.lang.Math.random()*99) ;
			arr.insert(n);
		}
		arr.display();
		arr.quickSort();
		arr.display();
	}
}