头与头之间的区别尾递归
我正试图区分这两种递归策略。
I'm trying to get the difference between these 2 recursive strategies.
我被告知的定义如下:
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,返回的值立即从调用函数返回
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
Head Recursion:当函数的第一个语句是递归调用时,调用是头递归的。
Head Recursion: A call is head-recursive when the first statement of the function is the recursive call.
在头部递归
中,递归调用,当它发生时,在函数中的其他处理之前出现(想想它发生在功能的顶部或头部)。
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).
在尾递归
中,它是相反的 - 处理发生在递归调用之前。在两种递归样式之间进行选择可能看似随意,但选择可能会产生重大影响。
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。先前展览的阶乘函数使用头部递归。一旦确定需要递归,它首先要做的是用递减的参数调用自身。
在路径末尾进行单个递归调用的函数使用尾递归。
参阅此文
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
递归示例:
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);
} | }
如果递归调用发生在方法的末尾,则称为尾递归
。尾递归类似于循环
。 方法在跳转到下一个递归调用之前执行所有语句
。
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开头,它被称为头递归。 方法在跳转到下一个递归调用之前保存状态
。
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
.