leetcode

Cpp and Python Solution for Leetcode with Basic idea. And the specific method is described in the first solution.

Title	Solution	Difficulty	Basic idea
1. Two Sum	Python	Easy	1. two-pointer 2. hashtable
7. Reverse Integer:star:	Python	Easy	1. mod and floor divide in Python3
12. Integer to Roman	Python	Medium	decode mapping with greedy thinking
13. Roman to Integer	Python	Easy	string traversal
20. Valid Parentheses	Cpp Python	Easy	stack
24. Swap Nodes in Pairs	Cpp	Medium	recursion
26. Remove Duplicates from Sorted Array	Python	Easy	double pointer
27. Remove Element	Python	Easy	double pointer
28. Implement strStr()	Python	Easy	double pointer
33. Search in Rotated Sorted Array	Python	Medium	binary search
53. Maximum Subarray	Python	Easy	DP
70. Climbing Stairs	Python	Easy	DP, recursive
80. Remove Duplicates from Sorted Array II	Python	Medium	two pointer
81. Search in Rotated Sorted Array II	Python	Medium	binary search
88. Merge Sorted Array	Python	Easy	two pointer, reverse insertion
91. Decode Ways	Python	Medium	DP
94. Binary Tree Inorder Traversal	Cpp Python	Medium	1. DFS recursion 2. explicit stack
118. Pascal's Triangle	Python	Easy	iter/recur
119. Pascal's Triangle II	Python	Easy	iter/recur
130. Surrounded Regions	Python	Medium	BFS-2dimension
133. Clone Graph	Cpp Python	Medium	1. DFS, visited hashmap 2. BFS: add all neighbors to queue and traverse
137. Single Number II	Python	Medium	bitwise
138. Copy List with Random Pointer	Python	Medium	1.backtracing 2.continuous copied node in space
150. Evaluate Reverse Polish Notation	Python	Medium	stack
153. Find Minimum in Rotated Sorted Array	Python	Medium	binary search
155. Min Stack	Cpp	Easy	1. two stack to store data and minimum 2. pair<data, minimum>, and var min to store current minimum.
168. Excel Sheet Column Title	Python	Easy	DFS iteration
171. Excel Sheet Column Number	Python	Easy	iteration 26-binary form
179. Largest Number	Python	Medium	sort through splicing two number as string
198. House Robber	Python	Medium	DP through the first two results of optimal solution
200. Number of Islands	Cpp Python	Medium	1. DFS: search to the depth of one element 2. BFS: search all neighbors of one element
204. Count Primes	Python	Easy	set multiple of prime as composite number through prime list
208. Implement Trie (Prefix Tree) ⭐	Python	Medium	root trie recursive
213. House Robber II	Python	Medium	divide two part to get local solution through DP
218. The Skyline Problem	Python	Hard	scan + priority-queue
220. Contains Duplicate III	Python	Medium	1. bisection
225. Implement Stack using Queues	Python	Easy	two queue operation to implement stack when pushing elements
231. Power of Two	Python	Easy	bitwise, n as divisor
232. Implement Queue using Stacks	Python	Easy	twice stack operation to implement queue
263. Ugly Number	Python	Easy	factorization through 2,3,5
264. Ugly Number II	Python	Medium	minimum heap
274. H-Index	Python	Medium	1. Dichotomy 2. Counter array
275. H-Index II	Python	Medium	1. Dichotomy 2. traverse
279. Perfect Squares	Cpp	Medium	BFS
300. Longest Increasing Subsequence	Python	Medium	DP
307. Range Sum Query - Mutable	Python	Medium	Segment Tree
342. Power of Four	Python	Easy	1. sqrt+powerOf2 2. Bitwise
344. Reverse String	Cpp/Python	Easy	1. double pointer 2. iteration or recursion of swap in place
345. Reverse Vowels of a String	Python	Medium	1. recursive with cache 2. DP
377. Combination Sum IV	Python	Medium	1. recursive with cache 2. DP
394. Decode String	Python	Medium	1. assistant stack 2. DFS
395. Longest Substring with At Least K Repeating Characters	Python	Medium	DC
421. Maximum XOR of Two Numbers in an Array	Python	Medium	bitwise
424. Longest Repeating Character Replacement	Python	Medium	slide window with two pointer - char number counter with list - r-l+1-window_maxn > k
448. Find All Numbers Disappeared in an Array	Python	Easy	~
451. Sort Characters By Frequency	Python	Medium	ordered dict
461. Hamming Distance	Python	Easy	XOR+NumberOf1
477. Total Hamming Distance	Python	Medium	Bitwise
485. Max Consecutive Ones	Python	Easy	traverse and find max_count: return max(max_count, count)
494. Target Sum	Cpp	Medium	1. DFS: enumerate all possibility
509. Fibonacci Number	Python	Easy	recur+hashmap (memerization to reduce repeated calculation)
561. Array Partition I	Python	Easy	sort and combine
567. Permutation in String	Python	Medium	slide window
576. Out of Boundary Paths	Python	Medium	1. DFS with memorization 2. DP
581. Shortest Unsorted Continuous Subarray	Python	Medium	1. sort and compare 2. find the law
633. Sum of Square Numbers	Python	Medium	1. enumeration 2. double pointer
643. Maximum Average Subarray I	Python	Easy	slide window, start pointer is outside of initial window
645. Set Mismatch	Python	Easy	count-array
665. Non-decreasing Array	Python	Easy	tranverse to find valley and judge index of i-1, i, i+1
692. Top K Frequent Words	Python	Medium	1. hashtable+sort 2. priority queue
697. Degree of an Array	Python	Easy	hashtable records [counts, left_one right_one]
703. Kth Largest Element in a Stream	Python	Easy	python heapq in no need of sorted operation
704. Binary Search♥	Python	Easy	1. two pointer 2. recursive
726. Number of Atoms	Python	Hard	stack with hashtable
739. Daily Temperatures	Python	Medium	Monotonic stack
740. Delete and Earn	Python	Medium	DP(rob house)
743. Network Delay Time	Python	Medium	Dijkstra
752. Open the Lock♥	Cpp	Medium	BFS: transform to graph to find the shortest path
783. Minimum Distance Between BST Nodes	Python	Easy	in-order traverse
832. Flipping an Image	Python	Easy	1. double pointer to reverse list 2. ^ XOR
872. Leaf-Similar Trees	Python	Easy	DFS yield
888. Fair Candy Swap	Python	Easy	hash table
896. Monotonic Array	Python	Easy	set inc and des flags
897. Increasing Order Search Tree	Python	Easy	in_order traversal
912. Sort an Array	Python	Medium	1. quick sort
930. Binary Subarrays With Sum	Python	Medium	1. Prefix sum 2. slide window
938. Range Sum of BST	Python	Easy	BFS, DFS
978. Longest Turbulent Subarray	Python	Medium	1. slide window 2. Dynamic Programming
993. Cousins in Binary Tree	Python	Easy	BFS, DFS (nonlocal)
1006. Clumsy Factorial	Python	Medium	1. stack to expression calculator with operator
1011. Capacity To Ship Packages Within D Days	Python	Medium	binary search with greedy thinking
1035. Uncrossed Lines	Python	Medium	2D-DP
1052. Grumpy Bookstore Owner	Python	Medium	1. slide window 生气的老板
1143. Longest Common Subsequence	Python	Medium	1. 2D-DP
1190. Reverse Substrings Between Each Pair of Parentheses	Python	Medium	1. stack/recursive
1310. XOR Queries of a Subarray	Python	Medium	XOR, prefix sum
1337. The K Weakest Rows in a Matrix	Python	Easy	Dichotomy+Mini-Heap
1418. Display Table of Food Orders in a Restaurant	Python	Medium	Hashtable
1423. Maximum Points You Can Obtain from Cards	Python	Medium	slide window + reverse thinking
1438. Longest Continuous Subarray With Absolute Diff Less Than or Equal to Limit	Python	Medium	slide window + sortedlist(sortedcontainer)
1442. Count Triplets That Can Form Two Arrays of Equal XOR	Python	Medium	XOR, prefix sum, mapping
1482. Minimum Number of Days to Make m Bouquets	Python	Medium	binary search with checkDay func
1486. XOR Operation in an Array	Python	Easy	XOR
1711. Count Good Meals	Python	Medium	hashtable, traverse targets
1720. Decode XORed Array	Python	Easy	XOR
1734. Decode XORed Permutation	Python	Medium	XOR
1736. Latest Time by Replacing Hidden Digits	Python	Easy	Greedy, bitwise judgement
1738. Find Kth Largest XOR Coordinate Value	Python	Medium	Prefix sum and sort
1818. Minimum Absolute Sum Difference	Python	Medium	bisect
1833. Maximum Ice Cream Bars	Python	Medium	sort+greedy
1893. Check if All the Integers in a Range Are Covered	Python	Easy	diff array + prefix sum
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LCP 07. 传递信息	Python	Easy	DFS
面试题 17.10. Find Majority Element LCCI	Python	Easy	Boyer-Moore vote algo to find mode