Sort Alghough

BubbleSort: each iteration exchange next two numbers to make the bigger one

SelectionSort: each iteration find out the min/max number

InsertSort:

ShellSort: by increment

MergeSort: recur sort & merge

QuickSort: from left to right find out the first bigger number while from right to left fund out the first smaller number until index i=j. compare the two found out numbers, exchange if left > right.

class QuickSort {
    public static void doQuickSort(int[] array, int left, int right) {
        if (left > right) {
            return;
        }
        int i = left;
        int j = right;
        int checkPoint = array[left];
        int temp;
        while(i < j) {
            // find out the first smaller number from right to left
            while (i < j && array[j] > checkPoint ) {
                j--;
            }
            System.out.println(" find out the first smaller number from right to left, array[" + j + "] is " + array[j]);

            // find out the first bigger number from left to right
            while(i < j && array[i] <= checkPoint) {
                i ++;
            }
            System.out.println(" find out the first bigger number from left to right, array[" + i + "] is " + array[i]);

            // exchange
            if (array[i] > array[j]) {
                temp = array[i];
                array[i] = array[j];
                array[j] =temp;
            }
        }

        System.out.print("This time array is: ");
        System.out.println(Arrays.toString(array));

        // exchange the first left number with the checkpoint number
        temp = array[left];
        array[left] = array[i];
        array[i] = temp;

        // sort the array from left to the partition index
        doQuickSort(array, left, i-1);

        // sort the array from partition index to the right
        doQuickSort(array, j+1, right);
    }
}

public class Test {

    public static void main(String[] args) {
        int[] array = {3, 2, 4, 1, 7, 7, 5 ,6 ,9 ,0};
        System.out.print("init array is: ");
        System.out.println(Arrays.toString(array));

        QuickSort.doQuickSort(array, 0, array.length-1);
    }
}

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