Leetcode打卡贴

leetcode刷题帖

激励自己，希望十月份之前成功跳槽，换个地方拧螺丝钉

Range Sum Query - immutable 前缀和数组
Range Sum Query - mutable 前缀和数组过了，其实是用线段树，哪天需要看一下
Evaluate Reverse Polish Notation 栈，遇到数字入栈，遇到符号出，计算之后再入栈，判断给的字符串是数字还是符号自己有个bug
Strobogrammatic Number

今天刷了
Top K Frequent Elements

Kth smallest Element in a sorted Matrix

Kth Largest in N arrays

Minimum size Subarray Sum

Longest Substring with at most K distinct characters

Number of Connected Components in an undirected Graph
Graph Valid Tree
Number of Island
三道都是纯BFS 改天试一下用Union Find

Kth Smallest Sum In Two Sorted Arrays （其实是 Kth smallest Element in a sorted Matrix 的变形）

Find K Pairs with Smallest Sums 与楼上同类型的题目，少加了一个corner case

Implement trie
N-ary preorder, postorder traversal
Map sum pairs卡住了  

min stack
Implement Queue using stacks
Decode String

Max stack

find the duplicate number 二分法
Wood cuts
Sqrt(x)

Copy books
Set mismatch
Binary Tree Maximum Path Sum (Divide & Conquer + traverse)

Validate Binary Search Tree
Flat binary tree to linked list
LCA