Java 头尾递归的区别
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The difference between head & tail recursion
提问by Scarl
I'm trying to get the difference between these 2 recursive strategies.
我试图找出这两种递归策略之间的区别。
The definition I was told is the following:
我被告知的定义如下：
Tail Recursion:A call is tail-recursive if nothing has to be done after the call returns i.e. when the call returns, the returned value is immediately returned from the calling function
尾递归：如果在调用返回后无需执行任何操作，则调用是尾递归的，即当调用返回时，返回值立即从调用函数返回
Head Recursion:A call is head-recursive when the first statement of the function is the recursive call.
头递归：当函数的第一条语句是递归调用时，调用是头递归的。
采纳答案by Java Curious ?
In head recursion, the recursive call, when it happens, comes before other processing in the function (think of it happening at the top, or head, of the function).
在 中head recursion，递归调用发生在函数中的其他处理之前（想想它发生在函数的顶部或头部）。
In tail recursion, it's the opposite—the processing occurs before the recursive call. Choosing between the two recursive styles may seem arbitrary, but the choice can make all the difference.
在 中tail recursion，情况正好相反——处理发生在递归调用之前。在两种递归风格之间进行选择似乎是随意的，但选择可以产生很大的不同。
A function with a path with a single recursive call at the beginning of the path uses what is called head recursion. The factorial function of a previous exhibit uses head recursion. The first thing it does once it determines that recursion is needed is to call itself with the decremented parameter. A function with a single recursive call at the end of a path is using tail recursion. Refer this article
具有在路径开头具有单个递归调用的路径的函数使用所谓的头递归。先前展示的阶乘函数使用头递归。一旦确定需要递归，它所做的第一件事就是用递减的参数调用自己。在路径末尾具有单个递归调用的函数使用尾递归。 参考这篇文章
Example Recursion :
示例递归：
public void tail(int n) | public void head(int n)
{ | {
if(n == 1) | if(n == 0)
return; | return;
else | else
System.out.println(n); | head(n-1);
|
tail(n-1); | System.out.println(n);
} | }
If the recursive call occurs at the end of a method, it is called a tail recursion. The tail recursion is similar to a loop. The method executes all the statements before jumping into the next recursive call.
如果递归调用发生在方法的末尾，则称为 a tail recursion。尾递归是similar to a loop。的method executes all the statements before jumping into the next recursive call。
If the recursive call occurs at the beginning of a method, it is called a head recursion. The method saves the state before jumping into the next recursive call.
如果递归调用发生在beginning of a method, it is called a head recursion. 的method saves the state before jumping into the next recursive call。
