PeterQiu0516 / LeetCode

My own solutions for LeetCode exercises.

LeetCode

My own practice for LeetCode exercise.

Dynamic Programming

#	Problem	Solution	Difficulty	Related Topics/Ideas
64	Minimum Path Sum	C++	Medium	2020/12/11 basic dp
72	Edit Distance	C++	Hard	2020/09/22 dp string, similar to 376 HW2
123	Best Time to Buy and Sell Stock III	C++	Hard	2020/08/16 daily exercise, dynamic programming, also comes with a neat solution
486	Predict the Winner	C++	Medium	2020/09/01 daily exercise, dynamic programming
546	Remove Boxes	C++	Hard	2020/08/15 daily exercise, dynamic programming
647	Palindromic Substrings	C++	Medium	2020/08/19 daily exercise, dynamic programming, & Manacher algorithm
877	Stone Game	C++	Medium	2020/09/01 daily exercise, dynamic programming, similar to 486, also comes with a trivial sol.
983	Minimum Cost For Tickets	C++	Medium	2020/08/25 daily exercise, dynamic programming, dfs

Divide and Conquer

#	Problem	Solution	Difficulty	Related Topics/Ideas
4	Median of Two Sorted Arrays	C++	Hard	O(log(m+n))Binary Search, Tricky Boundaries & Type conversion
15	3Sum	C++	Medium	While this problem has some trivial solutions, it is a good practice on Nesting Unordered Map (O(1) Search), which examines trade-off of search complexity and construction complexity
50	Pow(x, n)	C++	Medium	Fast Power Algorithm O(logn), overflow
101	Symmetric Tree	C++	Easy	280 In-class Exercise, Binary trees, recursion
148	Sort List	Python	Medium	Merge Sort, Linked List
436	Find Right Interval	C++	Medium	2020/08/27 daily exercise, binary search using map

Search

#	Problem	Solution	Difficulty	Related Topics/Ideas
17	Letter Combinations of a Phone Number	C++	Medium	2020/08/26 daily exercise, dfs
332	Reconstruct Itinerary	C++	Medium	2020/08/27 daily exercise, dfs & hash map, backtrack
491	Increasing Subsequences	C++	Medium	2020/08/25 daily exercise, subsequence, dfs
529	Minesweeper	C++	Medium	2020/08/20 daily exercise, basic dfs (do not use reference to modifies click).
679	24 Game	C++	Hard	2020/08/22 daily exercise, basic iteration & dfs
733	Flood Fill	C++	Easy	2020/08/16 daily exercise, basic dfs.
841	Keys and Rooms	C++	Medium	2020/08/31 daily exercise, basic dfs.
949	Largest Time for Given Digits	C++	Easy	2020/09/01 daily exericse, permutation, bfs
952	Largest Component Size by Common Factor	C++	Hard	2020/08/30 daily exercise, union find
967	Numbers With Same Consecutive Differences	C++	Medium	2020/08/18 daily exercise, basic bfs.
983	Minimum Cost For Tickets	C++	Medium	2020/08/25 daily exercise, dynamic programming, dfs

Greedy

#	Problem	Solution	Difficulty	Related Topics/Ideas
435	Non-overlapping Intervals	C++	Medium	2020/08/15 daily exercise, basic greedy algorithm.

Recursion

#	Problem	Solution	Difficulty	Related Topics/Ideas
101	Symmetric Tree	C++	Easy	280 In-class Exercise, Binary trees, recursion
105	Construct Binary Tree from Preorder and Inorder Traversal	C++	Medium	2020/12/01, tree construction, use index rather than construct new vector to save memory
148	Sort List	Python	Medium	Merge Sort, Linked List
589	N-ary Tree Preorder Traversal	C++	Easy	280 In-class Exercise, n-ary tree, recursion vs. iteration

Tree

#	Problem	Solution	Difficulty	Related Topics/Ideas
101	Symmetric Tree	C++	Easy	280 In-class Exercise, Binary trees, recursion
102	Binary Tree Level Order Traversal	C++	Medium	2020/12/07, level order traversal (bfs)
105	Construct Binary Tree from Preorder and Inorder Traversal	C++	Medium	2020/12/01, tree construction, use index rather than construct new vector to save memory
109	Convert Sorted List to Binary Search Tree	C++	Medium	2020/08/18 daily exercise, in-order traversal, median
110	Balanced Binary Tree	C++	Easy	2020/08/17 daily exercise, bottom-up recursion, avoid calculating height multiple times
111	Minimum Depth of Binary Tree	C++	Easy	2020/08/21 daily exercise, basic dfs (pay attention to leaf node)
404	Sum of Left Leaves	C++	Easy	2020/08/24 daily exercise, left leaf node.
437	Path Sum III	C++	Medium	2020/08/08 daily exercise, interesting recursion.
450	Delete Node in a BST	C++	Medium	2020/08/31 daily exercise, delete note recursively
589	N-ary Tree Preorder Traversal	C++	Easy	280 In-class Exercise, n-ary tree, recursion vs. iteration
987	Vertical Order Traversal of a Binary Tree	C++	Medium	2020/08/07 daily exercise, comp + recursion.
1032	Stream of Characters	C++	Hard	2020/08/23 daily exercise, union of chars, trie

Hash Map

#	Problem	Solution	Difficulty	Related Topics/Ideas
1	Two Sum	C++	Easy	280 In-class Exercise, Unordered Map (O(1) search)
15	3Sum	C++	Medium	While this problem has some trivial solutions, it is a good practice on Nesting Unordered Map (O(1) Search), which examines trade-off of search complexity and construction complexity
20	Valid Parentheses	C++	Easy	2020/08/14 daily exercise, stack & hash map (unordered_map)
211	Design Add and Search Words Data Structure	C++	Medium	2020/08/05 daily exercise, use unordered_map to realize dictionary with fast search
332	Reconstruct Itinerary	C++	Medium	2020/08/27 daily exercise, dfs & hash map, backtrack
409	Longest Palindrome	C++	Easy	2020/08/14 daily exercise, hash map (unordered_map)
705	Design HashSet	C++	Easy	2020/08/02 daily exercise, implement a hashset
771	Jewels and Stones	C++	Easy	Unordered Map, O(1) Search.
1032	Stream of Characters	C++	Hard	2020/08/23 daily exercise, union of chars, trie

Stack & Queue

#	Problem	Solution	Difficulty	Related Topics/Ideas
20	Valid Parentheses	C++	Easy	2020/08/14 daily exercise, stack & hash map (unordered_map)
933	Number of Recent Calls	C++	Easy	280 In-class Exercise, basic usage of queue

Linked List & Array

#	Problem	Solution	Difficulty	Related Topics/Ideas
21	Merge Two Sorted Lists	Python	Easy	Linked List
88	Merge Sorted Array	Python	Easy	Array
143	Reorder List	C++	Medium	Fast-slow pointer, reverse Linked List
148	Sort List	Python	Medium	Merge Sort, Linked List
442	Find All Duplicates in an Array	C++	Medium	2020/08/06 daily exercise, very interesting, no extra space and O(n) time.
491	Increasing Subsequences	C++	Medium	2020/08/25 daily exercise, subsequence, dfs
905	Sort Array By Parity	C++	Easy	2020/08/21 daily exercise, very interesting, no extra space and O(n) time.

String

#	Problem	Solution	Difficulty	Related Topics/Ideas
125	Valid Palindrome	C++	Easy	2020/08/03 daily exercise, tricky boundaries (upper & lowercase, distance between '0' and 'P')
171	Excel Sheet Column Number	C++	Easy	2020/08/09 daily exercise, reverse & base conversion
214	Shortest Palindrome	C++	Hard	2020/08/29 daily exercise, Manacher algorithm (for palindromic) + KMP algorithm (for searching substring with next[] represents last searched pos)
415	Add Strings	C++	Easy	280 In-class Exercise, Operation of big integers using string
459	Repeated Substring Pattern	C++	Easy	2020/08/24 daily exercise, substring, KMP algorithm (for searching substring with next[] represents last searched pos)
520	Detect Capital	C++	Easy	2020/08/01 daily exercise, basic string
557	Reverse Words in a String III	C++	Easy	2020/08/30 daily exercise, basic string
567	Permutation in String	C++	Medium	280 In-class Exercise, substring & sliding-window
647	Palindromic Substrings	C++	Medium	2020/08/19 daily exercise, dynamic programming, & Manacher algorithm (for palindromic)
824	Goat Latin	C++	Easy	2020/08/19 daily exercise, basic stringstream
949	Largest Time for Given Digits	C++	Easy	2020/09/01 daily exericse, permutation, bfs
1032	Stream of Characters	C++	Hard	2020/08/23 daily exercise, union of chars, trie

Basics & Math

#	Problem	Solution	Difficulty	Related Topics/Ideas
50	Pow(x, n)	C++	Medium	Fast Power Algorithm O(logn), overflow
119	Pascal’s Triangle II	C++	Easy	2020/08/12 daily exercise, combination
120	Triangle	C++	Medium	Minimum path sum
168	Excel Sheet Column Title	C++	Easy	280 In-class Exercise, funny but tricky number base conversion (not beginning from 0)
201	Bitwise AND of Numbers Range	C++	Medium	2020/08/23 daily exercise, bitwise AND & Brian Kernighan.
204	Count Primes	C++	Easy	Sieve of Euler, O(n)
258	Add Digits	C++	Easy	280 In-class Exercise, abc = a+b+c mod 9& Boundary conditions.
342	Power of Four	C++	Easy	2020/08/04 daily exercise, log and power
412	Fizz Buzz	C++	Easy	2020/08/26 daily exercise, mod
415	Add Strings	C++	Easy	280 In-class Exercise, Operation of big integers using string
470	Implement Rand10() Using Rand7()	C++	Medium	2020/08/28 daily exercise, random, reject sampling
497	Random Point in Non-overlapping Rectangles	C++	Medium	2020/08/22 daily exercise, random
551	Student Attendance Record I	C++	Easy	280 In-class Exercise
567	Permutation in String	C++	Medium	280 In-class Exercise, substring & sliding-window
657	Robot Return to Origin	C++	Easy	2020/08/28 daily exercise, simulation
969	Pancake Sorting	C++	Medium	2020/08/29 daily exercise, interesting sorting
1103	Distribute Candies to People	C++	Easy	2020/08/17 daily exercise, mod boundaries cases consideration
1200	Minimum Absolute Difference	C++	Easy	280 In-class Exercise
剑指 Offer 20	剑指 Offer 20. 表示数值的字符串	C++	Medium	2020/09/02 daily exercise, FSM, simulation