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<>一、递归概念
无限调用自身这个函数,每次调用总会改动一个关键变量,直到这个关键变量达到边界的时候,不再调用。
<>二、递归的三大要素
● 第一要素:明确你这个函数想要干什么(确定单层递归的逻辑)。先不管函数里面的代码什么,而是要先明白,你这个函数的功能是什么,要完成什么样的一件事。
●
第二要素:寻找递归结束条件(确定终止条件)。我们需要找出当参数为啥时,递归结束,之后直接把结果返回,请注意,这个时候我们必须能根据这个参数的值,能够直接知道函数的结果是什么。
●
第三要素:找出函数的等价关系式(确定递归函数的参数和返回值)。我们要不断缩小参数的范围,缩小之后,我们可以通过一些辅助的变量或者操作,使原函数的结果不变。
<>三、循环与递归
简单来说,循环是有去无回,而递归则是有去有回(因为存在终止条件)。
使用以下例子进行说明:
●
递归:你用你手中的钥匙打开一扇门,结果发现前方还有一扇门,紧接着你又用钥匙打开了这扇门,然后你又看到一扇们…但是当你开到某扇门时,发现前方是一堵墙无路可走了,你选择原路返回——这就是递归
● 循环:你用你手中的钥匙打开一扇门,结果发现前方也有一扇们,紧接着你又打开下一扇门…直到打开最后一扇门出去,或者一直没有碰到尽头
(死循环)——这就是循环。