Allows you to make changes to a document without altering its formatting.
The Writer is not a concrete class. Any object that implements write(), end(), and abort() can be a writer making it easy to adapt existing APIs or create specialized implementations without subclassing. There's no complex UnderlyingSink protocol with start(), write(), close(), and abort() callbacks that must coordinate through a controller whose lifecycle and state are independent of the WritableStream it is bound to.
，更多细节参见体育直播
* 核心思路：倒序单调栈（适配你的学习习惯），时间复杂度O(n)，空间复杂度O(n)
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