[REPOST]递归函数如何在合并排序中起作用？ [英] [REPOST] How recursive function works in merge sort ?

问题描述

void partition(int arr[],int low,int high){

    int mid;

    if(low<high){
        mid=(low+high)/2;
        partition(arr,low,mid);
        partition(arr,mid+1,high); // How does the recursion work here?
        mergeSort(arr,low,mid,high);
    }
}

谢谢，mahbub

Thanks, mahbub

推荐答案

它的工作原理就像递归一样功能呢。在这种特殊情况下，分区在数组的连续半范围内调用自身（直到范围退化为单个项目，这是其递归的停止条件）。我建议你用纸和铅笔模拟函数调用，使用短数组作为输入。

Well it works like recursive functions do. In this particular case partition call itself on successive half-ranges of the array (until the range degenerates to a single item, this is the stop condition of its recursion). I suggest you to simulate the function calls with paper and pencil using a short array as input.

亲爱的朋友：



递归merge_sort的工作原理如下：

1-数组A []（长度为n）------> 2数组：数组a1 []（用lengs n / 2）

数组a2 []（长度为n / 2）



数组A []（长度为n）：低----中----高



a1 []（长度为n / 2）：低 - --mid

a2 []（长度为n / 2）：mid + 1 ---- high







2 - 然后对每个数组进行排序（a1 []和a2 []）

a1 []：低---- mid

a2 []：mid + 1 ---- high



3-then merger（join）2排序数组（a1 []&a2 [] ）直到我们获得1个排序数组（A []​​）

并且在每个步骤中：



1- mid =（低+高）/ 2;找到阵列的中心



2-分区（arr，低，中）;排序数组A []的下半部分---- mid



3-分区（arr，mid + 1，high）;排序数组的上半部分A [] mid + 1 ---- high



4- mergeSort（arr，low，mid，high）;合并两个分类的部分





好​​luk

Dear Friend:

recursive merge_sort works as the following steps:
1- array A[] (with length n) ------> 2 array : array a1[] (with lengs n/2)
array a2[] (with length n/2)

array A[] (with length n): low----mid----high

a1[] (with length n/2) : low----mid
a2[] (with length n/2) : mid+1---- high



2-then sort each of arrays(a1[] & a2[])
a1[] : low----mid
a2[] : mid+1---- high

3-then merger(join) 2 sorted array(a1[] & a2[]) until we obtain 1 sorted array (A[])
and in each of steps :

1- mid=(low+high)/2; finding the center of array

2- partition(arr,low,mid); sorting the lower half of array A[] low----mid

3- partition(arr,mid+1,high); sorting the upper half of array A[] mid+1----high

4- mergeSort(arr,low,mid,high); merging two sorted parts


Good luk

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