Month: December 2018

Link: https://leetcode.com/problems/flip-equivalent-binary-trees/  Thought If 2 nodes are equivalent, either their left and right side match, or they are flipped match. So using a recursion(why recursion? It is a Tree!), and try to match each node pairs from root1 and root2. For each recursion level, I will first compare if current node pair have the same value. […]

link: https://leetcode.com/problems/reveal-cards-in-increasing-order/ Thought So the rule is if you pop anything from front, then you shall move next head to tail. Reversely, if we want to build the original sequence, we could assume if you want to insert anything in head, you should pop your tail, and push the tail to head Code Runtime Time: O(n)Space: […]

link: https://leetcode.com/problems/largest-time-for-given-digits/ Thought Its easy to think use DFS to solve it: it has limit data(4 digits), and DFS will enumerates all possible combinations Code Runtime Time: O(n!)Space: O(n!)