缺大米的请参加这个刷题/Mock interview活动

补昨天day 23

lc新5， review5
319. Bulb Switcher
square root of the input，背后的思想是一个灯泡被开关奇数次才会亮，divisor 是成对出现的，只有i是square才会是奇数次


240. Search a 2D Matrix II
从右上角找到左下角～

48. Rotate Image
从四个角开始swap

723. Candy Crush
先找到连续的cell， 从下往上遍历

333. Largest BST Subtree
bottom up dfs

06/24
打卡第16天

• Least Moves To Asceding Array
• Unique binary search tree
• Unique binary search tree II
• Longest Substring With K Typed Characters

补前天 day22

lc new 5 review 10+
622. Design Circular Queue
注意检查capacity！

536. Construct Binary Tree from String
分类讨论四个case： -，（，），数字

334. Increasing Triplet Subsequence
就很精妙，两个变量存 小和大，找到更大的就可

152. Maximum Product Subarray
三个变量min，max，res，遍历更新（因为要考虑负数和0

662. Maximum Width of Binary Tree
用map存每一层第一个节点的col idx， 用 最后一个节点的idx减去它就是每层的width

6.24 打卡6道dp

今天的四题

打卡第23天， 刷了3道题

2. Add Two Numbers
linked list, 注意l1, l2 是否是null

19. Remove Nth Node From End of List
用2个指针，第一个指针指向list的前端，另一个和前一个差n位置

24. Swap Nodes in Pairs
linked list, 先判断head.next, head.next.next是否存在，然后互调。

打卡第十四天
101， 104，111

中间准备答辩耽误了，继续打卡

Day 2, solved 6 problems.

Tips:
1. Integer operations such as +, -, *, / should avoid overflow by type cast to long. e.g., LC 235;
2. If we want to find the target within the iteration loop of binary search, do NOT forget = in the loop conditional;
e.g., in LC 4, while (lo <= hi), where the '=' is a must;
3. Use dummy node for ListNode problems when necessary; e.g., LC 2.


补充内容 (2020-6-27 01:21):
抱歉，发重复了，没法删除，请忽略。

Day 2, solved 6 problems.

Tips:
1. Integer operations such as +, -, *, / should avoid overflow by type cast to long. e.g., LC 235;
2. If we want to find the target within the iteration loop of binary search, do NOT forget = in the loop conditional;
e.g., in LC 4, while (lo <= hi), where the '=' is a must;
3. Use dummy node for ListNode problems when necessary; e.g., LC 2.