[第二期活动] 在职刷题打卡，目标工作日一天2题，周末一天5题

#Day_22

Finished * 2, 水一道
Divide Two Integers
Merge Two Sorted Lists

Day 17
349 & 350, intersection of two arrays, hash table / two pointer
485, 487, 1004 max consecutive ones, sliding window
53, maximum subarray, the max is could either end at this point or start at this point.
238, product of array except self, two pass
278, first bad version, binary search

day 20
Populating Next Right Pointers in Each Node
Binary Tree Right Side View

#Day_9

1165. single-row keyboard
1166. design-file-system
1167 minimum cost to connect sticks

#Day_23

Finished * 2
Insert Interval
Jump Game II

day 2
merge overlapping intervals
sum of two values
reversed a singly-linked list

打卡Day 5 前两天在旅行就没有刷题

309. Best Time to Buy and Sell Stock with Cooldown - DP 从O(n)时间O(n)空间优化到O(n)时间O(1)时间, leveraging the fact that each state only depends on the previous 2 states, which could be stored in variables.
11. Container With Most Water - Two pointers.
42. Trapping Rain Water - DP 从O(n)时间O(n)空间优化到O(n)时间O(1)时间, as we only need to keep track of the left highest and right highest.
334. Increasing Triplet Subsequence - 从O(n)时间O(n)空间优化到O(n)时间O(1)时间 - 最佳solution还是挺巧妙的
128. Longest Consecutive Sequence - 巧妙利用hash set
164. Maximum Gap - pigeon hole principle and bucket sort. Even if the numbers are uniformly distributed, the gap would be (max-min)//(len(nums)-1). Therefore, if we set the bucket size to be that, we can ensure that the maximum gap never happens within one single bucket. We can only compare among the buckets.
287. Find the Duplicate Number - 可以用finding the duplicate element in a linked list的方法来做。注意当fast遇到slow的时候，他们并不一定处于loop的开端。所以我们需要用另一个loop来得出loop的开端。

day 21
今天5题
Binary Tree Maximum Path Sum
Populating Next Right Pointers in Each Node II
Reverse Linked List
Binary Tree Upside Down
Construct Binary Tree from Preorder and Inorder Traversal

Day_11 (8/23)
Longest Palindrome
Maximum Subtree

day 22
今日5题
Diameter of Binary Tree
Verify Preorder Serialization of a Binary Tree
Construct Binary Tree from Inorder and Postorder Traversal
Path Sum II
Path Sum