Monotonic Stack(单调栈) https://github.com/labuladong/fucking-algorithm/blob/master/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E7%B3%BB%E5%88%97/%E5%8D%95%E8%B0%83%E6%A0%88.md
https://leetcode.com/discuss/interview-question/352460/Google-Online-Assessment-Questions
Patience sorting https://www.cs.princeton.edu/courses/archive/spring13/cos423/lectures/LongestIncreasingSubsequence.pdf https://en.wikipedia.org/wiki/Patience_sorting