原始网址:
http://www.careercup.com/question?id=248673
题目:
Given a document and a query of K words,
how do you find the smallest window that covers all the words at least once
in that document?
(given you know the inverted lists of all K words, that is, for each word,
you have a list of all its occurrrences).
Could someone propose an algorithm in O(n)?
假设 occurrrences lists 是 sorted, 用 TreeMap 应可在 O(N*logK) 解决,
一开始将每个 occurrrences list 最小的丢入 TreeMap 就可得到第一个 window,
(key = index in the document, value = the occurrrences list it belonged & its
index in that occurrrences list),
之后将 TreeMap 最小的移除并加入同一个 occurrrences list 的下一个即可移动
window,
直到任一个 occurrrences list 耗完.
但要在 O(N) 的时间内解决就想不出来了...
不知道板上有没有人有什么 idea?