在职刷题备战打卡～～

工作之后就没怎么刷题了，如今重新磨刀，准备再战，立贴督促自己加油⛽️. 和地里的朋友们一起备战分类数据结构算法，面经，system design
LC status:
280 / 1019 Solved

736Todo

SF
759. Employee Free Time
Sweep line

751 IP to CIDR, 主要就是子网掩码的计算，考察了位操作，long ip to string, string ip to long, Long.lowestOneBit()
269. Alien Dictionary, topological sort, 需要用到priority queue来确保最终输出顺序, 注意corner case

787. Cheapest Flights Within K Stops , BFS, 注意边界条件是否更新一个city cost based on current stops , if next stop matching dest
755. Pour Water, 数组操作，左边扫一次往右边回溯，右边扫一次往左边回溯，比较注重细节
251. Flatten 2D Vector, 2 pointers, 1 for current row, another for current column, both much be valid at any given time
756. Pyramid Transition Matrix, 暴力搜索 DFS, 另外一种状态压缩利用二位整型数组的没搞懂。。。
409. Longest Palindrome, 解法1 hashmap, 解法2用 int array count

Find K Closest Elements, 解法1 sort, 解法2 binary search + 2 pointer
Palindrome Pairs, Trie, 需要正向逆向扫两边，注意去重复
Word Search II, DFS + trie prune
一些可以用二分法的题pow, minimum in rotated sort array, search in rotated sorted array, first bad version