效率：递归与循环 [英] Efficiency: recursion vs loop

问题描述

这只是出于好奇，但更有效的是递归还是循环？

This is just curiosity on my part, but what is more efficient, recursion or a loop?

给出两个函数（使用通用的lisp）：

Given two functions (using common lisp):

(defun factorial_recursion (x)
    (if (> x 0)
        (* x (factorial_recursion (decf x)))
        1))

和

(defun factorial_loop (x)
    (loop for i from 1 to x for result = 1 then
        (* result i) finally
        (return result)))

哪个效率更高？

推荐答案

我什至不必阅读您的代码。

I don't even have to read your code.

循环对于阶乘而言更为有效。进行递归时，堆栈上最多有 x 个函数调用。

Loop is more efficient for factorials. When you do recursion, you have up to x function calls on the stack.

出于性能原因，您几乎从不使用递归。您可以使用递归使问题更简单。

You almost never use recursion for performance reasons. You use recursion to make the problem more simple.

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