合并排序（递归拆分数组） [英] Merge sort(splitting array recursively)

问题描述

这是一个递归地将数组拆分成子集的函数。

我的问题是我不明白该函数将如何递归两次 .. Isn' t应该首先用新参数（a，i，mid）递归 ..如果已经破坏，它将如何返回并获取新参数（a，mid + 1，j）在第一个地方递归？



我尝试过：

this is a function that split the array into subsets recursively ..
My problem is that I don't understand how the function will recurse twice..Isn't is supposed to recurse first with new arguments(a,i,mid).. how will it then return and take new arguments(a,mid+1,j) if it already broke to recurse at first place?

What I have tried:

void mergesort(int a[],int i,int j)
{
int mid;
if(i<j)
{
mid=(i+j)/2;
mergesort(a,i,mid); //left recursion
mergesort(a,mid+1,j); //right recursion//my problem//
merge(a,i,mid,mid+1,j); //merging of two sorted sub-arrays
}
}

推荐答案

Quote：

我不明白该函数将如何递归两次。

I don't understand how the function will recurse twice.

您的代码不会同时重复两次，它按顺序重复2次。

Your code don't recurs twice at same time, it recurs 2 times in sequence.

mergesort routine execution
  do stuff
  call mergesort(a,i,mid); // first recurs
  resume // resume execution when first recurs is finished
  do stuff
  call mergesort(a,mid+1,j); // second recurs
  resume // resume execution when second recurs is finished
  do stuff

使用调试器查看代码执行

有一个工具可以让你看到你的代码在做什么，它的名字是调试器。它也是一个很好的学习工具，因为它向你展示了现实，你可以看到哪种期望与现实相符。

当你不明白你的代码在做什么或为什么它做它做的时候，答案就是答案是调试器。

使用调试器查看代码正在执行的操作。只需设置断点并查看代码执行情况，调试器允许您逐行执行第1行并在执行时检查变量。



调试器 - 维基百科，免费的百科全书 [ ^ ]



掌握Visual Studio 2010中的调试 - 初学者指南 [ ^ ]

使用Visual Studio 2010进行基本调试 - YouTube [ ^ ]

调试器在这里向您展示您的代码正在做什么，您的任务是与什么进行比较应该这样做。

调试器中没有魔法，它没有找到错误，它只是帮助你。当代码没有达到预期的效果时，你就会接近一个错误。

Use the debugger to see the code execute
There is a tool that allow you to see what your code is doing, its name is debugger. It is also a great learning tool because it show you reality and you can see which expectation match reality.
When you don't understand what your code is doing or why it does what it does, the answer is debugger.
Use the debugger to see what your code is doing. Just set a breakpoint and see your code performing, the debugger allow you to execute lines 1 by 1 and to inspect variables as it execute.

Debugger - Wikipedia, the free encyclopedia[^]

Mastering Debugging in Visual Studio 2010 - A Beginner's Guide[^]
Basic Debugging with Visual Studio 2010 - YouTube[^]
The debugger is here to show you what your code is doing and your task is to compare with what it should do.
There is no magic in the debugger, it don't find bugs, it just help you to. When the code don't do what is expected, you are close to a bug.

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