21归并排序、计数排序、桶排序、基数排序

#include<stdio.h>
#include<stdlib.h>

void merge_sort(int arr[], int first, int last)
{
    int mid= 0;
    if(first<last)
    {
        mid = (first+last)/2;
        //分下标
        merge_sort(arr,first,mid);
        merge_sort(arr,mid+1,last);
        //对于分开的元素做处理
        merge(arr,first,mid,last);
    }
}

void merge(int arr[], int first, int mid, int last)
{
    int k=0;
    int *temp=(int *)malloc((high-low+1)*sizeof(int));
    //申请空间用来存放之后排序的内容
    int left_low = low;
    int left_high = mid;
    int right_low = mid+1;
    int right_high = high;
    //记录左右的头尾
    for(int i=0;left_low<=left_high && right_low<=right_high;i++)
    {
        if(arr[left_low]<=arr[right_low])
            temp[i]=arr[left_low++];	//排序并存入数组
        else
            temp[i]=arr[right_low++];
        k++;
	}
    //三种情况：正好全部跑完、左边结束、右边结束
    if(left_low<=left_high)
    {
        for(int i=left_low;i<left_high;i++)
        {
            temp[k]=arr[i];
		}
    }
    if(right_low<=right_high)
    {
        for(int i=right_low;i<right_high;i++)
        {
            temp[k]=arr[i];
		}
    }
    
    //将新数组的内容放回原数组
    for(int i=0;i<high-low+1;i++)
    {
        arr[low+1] = temp[i++];
    }
    free(temp);
}