基本排序算法的实现

package com.dongbin.sort;

import java.util.Arrays;

/**
 * 排序
 * @author dongbin
 *
 */
public class AllSort {
    
    public static void main(String[] args) {
        int[] arr = {1,32,43,11,23,45};
        MergeSort(arr);
        System.out.println(Arrays.toString(arr));
    }

    /**
     * 冒泡排序
     * @param arr
     * @return
     */
    public static int[] BubbleSort(int[] arr){
        
        for(int i=0;i<arr.length-1;i++){
            for(int j=i+1;j<arr.length;j++){
                if(arr[i]>arr[j]){
                    int temp = arr[i];
                    arr[i] = arr[j];
                    arr[j] = temp;
                }
            }
        }
        return arr;
    }
    
    /**
     * 选择排序
     * @param arr
     * @return
     */
    public static int[] SelectionSort(int[] arr){
        
        int min;
        for(int i=0;i<arr.length-1;i++){
            min=i;
            for(int j=i+1;j<arr.length;j++){
                if(arr[i]>arr[j]){
                    min = j;
                }
            }
            
            if(min!=i){
                int temp = arr[i];
                arr[i] = arr[min];
                arr[min] = temp;
            }
        }
        return arr;
    }
    
    /**
     * 插入排序
     * @param arr
     * @return
     */
    public static int[] InsertSort(int[] arr){
        
        for(int i=1;i<arr.length;i++){
            int current = arr[i];
            int pos = i;
            for(int j=i-1;j>=0;j--){
                if(arr[j]>current){
                    arr[j+1] = arr[j];
                    pos = j;
                }
            }
            arr[pos]=current;
        }
        return arr;
    }
    
    /**
     * 快速排序
     * @param arr
     * @return
     */
    public static int[] QuickSort(int[] arr){
        if(arr.length<=1){
            System.out.println("传入的数组长度小于或等于1");
        }else{
            _quickSort(arr, 0, arr.length-1);
        }
        
        return arr;
    }
    
    public static void _quickSort(int[] arr ,int start, int end){
        if(start>=end){
            return;
        }
        
        int i = start,j=end,current = arr[j];
        boolean flag = false;
        
        while(i!=j){
            if(flag){
                if(arr[j]<current){
                    int temp = arr[j];
                    arr[j] = arr[i];
                    arr[i] = temp;
                    flag = false;
                }else j--;
            }else{
                if(arr[i]>current){
                    int temp = arr[j];
                    arr[j] = arr[i];
                    arr[i] = temp;
                    flag = true;
                }else i++;
            }
        }
        
        _quickSort(arr, start, i-1);//左边
        _quickSort(arr, j+1, end);//右边
    } 
    
    
    /**
     * 归并排序
     * @param arr
     * @return
     */
    public static int[] MergeSort(int[] arr){
        _mergeSort(arr, 0, arr.length-1);
        return arr;
    }
    
    public static void _mergeSort(int[] arr,int left,int right){

        if (left < right) {
            int mid = (left + right) / 2;
            // 划分
            _mergeSort(arr, left, mid);
            _mergeSort(arr, mid + 1, right);

            // 合并
            _merge(arr, left, mid, right);
        }

    }
    public static void _merge(int[] arr,int left,int mid,int right){
        
        int[] newArr = new  int[arr.length];//新数组
        int center = mid+1;
        int tmp = left;
        int pos = left;
        
        while(left<=mid&&center<=right){
            if(arr[left]<=arr[center]){
                newArr[pos++]=arr[left++];
            }else{                
                newArr[pos++]=arr[center++];
            }
        }
        
        while(left<=mid){
            newArr[pos++]=arr[left++];
        }
        
        while(center<=right){
            newArr[pos++]=arr[center++];
        }
        
        while(tmp<=right){
            arr[tmp] = newArr[tmp++];
        }
        
        
        
    }
}