归并和快排

package com.ma;//归并

import java.util.Arrays;

public class MergeSort {
    public static void mergeSort(int[] a){
        int[] result = merge(a);
        for (int i = 0; i < a.length; i++) {
            a[i] = result[i];
        }

    }


    public static int[] merge(int[] a){
        if(a.length == 1)
            return a;
        int mid = a.length/2;
        int[] left = Arrays.copyOfRange(a,0,mid);
        int[] right = Arrays.copyOfRange(a,mid,a.length);
        return sort(merge(left),merge(right));
    }


    private static int[] sort(int[] left, int[] right){
        int[] result = new int[left.length+right.length];
        int leftPointer = 0;
        int rightPointer = 0;
        for (int i = 0; i < result.length; i++) {
            if(leftPointer == left.length){
                result[i] = right[rightPointer++];
                continue;
            }
            if(rightPointer == right.length){
                result[i] = left[leftPointer++];
                continue;
            }
            if(left[leftPointer] <= right[rightPointer]){
                result[i] = left[leftPointer++];
            }else{
                result[i] = right[rightPointer++];
            }
        }
        return result;
    }
}

快排

    快排
    public static void quickSort(int[] a) {
        sort(a, 0, a.length - 1);
    }
    private static void sort(int[] a , int start ,int end){
        if(start == end){
            return;
        }
        int pivot = a[start];
        int leftPointer = start;
        int rightPointer = end;
        while(leftPointer != rightPointer){
            while(leftPointer < rightPointer && a[rightPointer] >= pivot){
                rightPointer--;
            }
            while (leftPointer < rightPointer && a[leftPointer] < pivot){
                leftPointer++;
            }
            if(leftPointer < rightPointer){
                Util.swap(a,leftPointer,rightPointer);
            }
        }
        Util.swap(a,start,leftPointer);
        sort(a,start,leftPointer);
        sort(a,leftPointer+1,end);
    }