组队复习算法+刷题

打卡
leetcode 66

8.10打卡：
340. Longest Substring with At Most K Distinct Characters => Sliding Window: map<char, lastIdx>, when map.size() > k, remove char with min lastIdx
98. Validate Binary Search Tree => recursion: lower and upper bound
621. Task Scheduler => no. of intervals = no. of tasks + no. of idles (depends on task with max frequency)
125. Valid Palindrome => two pointers
158. Read N Characters Given Read4 II - Call multiple times => use pointers and temp buffer to record the reading pregress
133. Clone Graph => similar with copy list with random pointer but use recursion: map<original node, cloned node>
348. Design Tic-Tac-Toe => rows[], cols[], diagonal and anti-diagonal to check if a player wins
199. Binary Tree Right Side View => Recursion: maintain currDepth to check if any node is added at current level

好厉害， 希望自己也开始努力

打卡
1. [457] Circular Array Loop （fast-slow pointers）
2. [464] Can I Win (Top-Down DP, memorization, 好几道游戏的题目都是这种思路 类似还有 1140-Stone Game II)
3. [467] Unique Substrings in Wraparound String （DP - 记录连续字符个数）

Day 3 打卡
9. Palindrome Number [Math] - easy
771. Jewels and Stones [HashSet] - easy

8/10
周六还要带娃出去玩，只刷一道250的题
250. Count Univalue Subtrees

8.11打卡：
314. Binary Tree Vertical Order Traversal => TreeMap + Queue BFS + column index
349. Intersection of Two Arrays => hashset
953. Verifying an Alien Dictionary => indices[26], comaring each two of consecutive words to find first difference
543. Diameter of Binary Tree => recursion get depth
173. Binary Search Tree Iterator => stack to simulate recursion
278. First Bad Version => binary search
680. Valid Palindrome II => (left, right-1) || (left+1, right)
157. Read N Characters Given Read4 => min(n - readPtr, currReadBytes)

打卡4:
Array:
4. Median of Two Sorted Arrays
String:
28        Implement strStr()       
14        Longest Common Prefix       
58        Length of Last Word

8/11
207.course-schedule.java --> Topology sort

8.12打卡：
896. Monotonic Array => two boolean flags to check whether increasing/decreasing
438. Find all Anagrams in a String => Sliding window + hashMap<char in pattern, freq of char> + counter to make sure window contains needed chars
211. Add and Search Word - Data structure design => Trie + DFS