缺大米的请参加这个刷题/Mock interview活动

day 10  7道题
210. Course Schedule II  follow up  topological sort all paths    backtrack + bfs       
516. Longest Palindromic Subsequence  dynamic programming       
Find Largest Value in Each Tree Row dfs or bfs       
513. Find Bottom Left Tree Value dfs or bfs
491. Increasing Subsequences iterative construct or dfs       
329. Longest Increasing Path in a Matrix  dfs+dp
996. Number of Squareful Arrays : backtrack  search dictionary of s, to avoid duplicate       

第一天打卡，刷了3个hard

Day 13打卡：3题

day 9-- 9道题
809. Expressive Words        groupby, staightforward
477. Total Hamming Distance  loop over bits    "{:032b}".format(num)
1123. Lowest Common Ancestor of Deepest Leaves  DFS while return two value (depth, common ancestor). for each node, if  left node depth is equal to right node depth, then common ancestor is current node, else  common ancestor is the dfs of higher depth son.
481. Magical String  straight forward.  list.count()  function
486        Predict the Winner     dp from up to bottom        
518. Coin Change 2  outer loop coin inner loop amount.  similar with knapsack problem.  different with combination V.
484  Find Permutation   stack or two pointer        
487. Max Consecutive Ones II two pinters        
490. The Maze bfs

Day 1 - 今天做了6道 tree的题，都不是很难，找找手感
Binary Search Tree Iterator - 实现起来很容易，主要是要想到把一串left child都push进stack
Merge Two Binary Trees - 简单题，偷了个懒在其中一个tree是null的时候之间返回另一个tree了
Invert Binary Tree - 简单题，记得刚开始接触recursion的时候，这道题都卡了很久
Unique Binary Search Trees - 画一画就能发现规律，排列组合算是个dp题
Maximum Depth of Binary Tree  - 练手题
Same Tree - 也是练手题

打卡第十二天

今天做了三题，谢谢啦

刷题第一天，发现全都忘干净了，依然处于热身阶段。希望以后速度会有所恢复。

Day 7:

Day 10, 06/14/2020, SQL, 10 solved.

Have to refresh my SQL skills, start from easy queries.