排序

题目描述

给定一个数组，请你编写一个函数，返回该数组排序后的形式

输入：[5,2,3,1,4]

返回值由小到大：[1,2,3,4,5]

返回值由大到小：[5,4,3,2,1]

package com.refinitiv.ciqm.udf;

import java.util.*;

public class Solution {
    
    public static void main(String[] args) {
        int[] arr = {5,2,3,1,4,7,8};
        Solution sl = new Solution();
//         从大到小快速排序
        quickSortBigtoSmall(arr,0,arr.length-1);
//         从小到大快速排序
        quickSortSmalltoBig(arr,0,arr.length-1);
        System.out.println(Arrays.toString(arr));
    }

    private static void quickSortSmalltoBig(int[] arr,int low,int high){
        if (low < high){
            int mid = getIndexFromSmallToBig(arr,low,high);
            quickSortSmalltoBig(arr,low,mid-1);
            quickSortSmalltoBig(arr,mid +1 ,high);
        }
    }

    private static int getIndexFromSmallToBig(int[] arr,int low,int high){
        int index = (low + high) /2;
        int midNum = arr[index];
        
        swap(arr,index,high);
        System.out.println("swap1" + Arrays.toString(arr));
        while(low < high){
            while(low < high && arr[low] <= midNum) {
                low++;
                
            }
            swap(arr,low,high);
            
            while (low < high && arr[high] >= midNum) {
                high--;
                
            }
            swap(arr,low,high);
        }
        return high;
    }

    private static void quickSortBigtoSmall(int[] arr,int low,int high) {
        if(low<high){
            // 获取中间点
            int mid = getIndexFromBigToSmall(arr,low,high);
            quickSortBigtoSmall(arr,low,mid -1);
            quickSortBigtoSmall(arr,mid+1,high);
        }
    }

    private static int getIndexFromBigToSmall(int[] arr,int low,int high){
        int index = (low + high) / 2;
        int midNum = arr[index];
        // 无论取的值是哪一个 ，都应该将其放在最后面
        swap(arr,index,high);
        
        while (low < high){

            //左侧值大于或者等于左侧值时,只需要移动指针即可
            while (low < high && arr[low] >= midNum) {
                low++;
            }
            swap(arr,low,high);
            
            //右侧小于或者等于右侧值是，只需要移动指针即可
            while (low < high && arr[high] <= midNum) {
                high--;
            }
            swap(arr,low,high);
        }

        return high;
    }

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

}