快速排序

　　　　拆分数组，以最右侧为轴，小于轴的元素数组左侧，大于轴的元素数组右侧，将轴元素移到中央。

public class QuickSort {
    public static void main(String[] args) {
        int[] arr = {7, 3, 2, 8, 1, 9, 5, 4, 6};
        sort(arr, 0, arr.length - 1);
        print(arr);
    }

    /**
     * 快速排序
     *
     * @param arr
     */
    private static void sort(int[] arr, int leftBound, int rightBound) {
        partition(arr, leftBound, rightBound);
    }

    private static void partition(int[] arr, int leftBound, int rightBound) {
        int pivot = arr[rightBound];// 杠杆元素，最右侧元素
        int left = leftBound; // 左侧开始元素
        int right = rightBound - 1; // 右侧开始元素
        while (left < right) {
            while (left < right && arr[left] <= pivot) {
                left++;
            }
            while (left < right && arr[right] >= pivot) {
                right--;
            }
            if (left < right) {
                swap(arr, left, right);
            }
        }
        swap(arr, left, rightBound);
    }

    private static void swap(int[] arr, int i, int j) {
        int temp = arr[i];
        arr[i] = arr[j];
        arr[j] = temp;
    }

    private static void print(int[] arr) {

        for (int i : arr) {
            System.out.print(i + " ");
        }
    }
}

　　加入递归处理

package com.example.sort.quick;

public class QuickSort {
    public static void main(String[] args) {
        int[] arr = {7,3,2,10,8,1,9,5,4,6};
        sort(arr, 0, arr.length - 1);
        print(arr);
    }

    /**
     * 快速排序
     *
     * @param arr
     */
    private static void sort(int[] arr, int leftBound, int rightBound) {
        if (leftBound >= rightBound) return;
        int mid = partition(arr, leftBound, rightBound);
        sort(arr, leftBound, mid - 1);
        sort(arr, mid + 1, rightBound);
    }

    private static int partition(int[] arr, int leftBound, int rightBound) {
        int pivot = arr[rightBound];// 杠杆元素，最右侧元素
        int left = leftBound; // 左侧开始元素
        int right = rightBound - 1; // 右侧开始元素
        while (left <= right) {
            while (left <= right && arr[left] <= pivot) {
                left++;
            }
            while (left <= right && arr[right] > pivot) {
                right--;
            }
            if (left < right) {
                swap(arr, left, right);
            }
        }
        swap(arr, left, rightBound);
        return left;
    }

    private static void swap(int[] arr, int i, int j) {
        int temp = arr[i];
        arr[i] = arr[j];
        arr[j] = temp;
    }

    private static void print(int[] arr) {

        for (int i : arr) {
            System.out.print(i + " ");
        }
    }
}

　　java默认排序，双轴快排

　　...