Any seemingly pointless activity which is actually necessary to solve a problem which solves a problem which, several levels of recursion later, solves the real problem you're working on.
任何看似毫无意义的行为，实际上是要解决一个问题，却要先解决与这个问题相关的问题，来回折腾好几次之后，才能解决你真正需要解决的问题。
