pub struct Solution;
剑指 Offer 46. 把数字翻译成字符串 https://leetcode.cn/problems/ba-shu-zi-fan-yi-cheng-zi-fu-chuan-lcof/
TypeId
self
Returns the argument unchanged.
Calls U::from(self).
U::from(self)
That is, this conversion is whatever the implementation of From<T> for U chooses to do.
From<T> for U