Learn

Something I have learned...

Algorithm

Title	Solution
Array	20.py Valid Parentheses (elegant coding) 38.py Count and Say (count consecutive elements) 42.py Trapping Rain Water (two pointers) 45.py Jump Game II (till and farest reach) 155.py Min Stack 209.py Summary Ranges (left pointer and accumulate) 217.py Contains Duplicate (set) 219.py Contains Duplicate II (just cares last) 228.py Summary Ranges (count consecutive elements) 238.py Product of Array Except Self (left2right, right2left) 242.py Valid Anagram (counter equality) 348.py Design Tic-Tac-Toe (diagonal math, sum, loop else) 349.py Intersection of Two Arrays (set & set) 350.py Intersection of Two Arrays II (counter & counter) 388.py Longest Absolute File Path (split, lstrip, memorization) 838.py Push Dominoes (force propagate/reset) 859.py Buddy Strings (enumerate cases) 1002.py Find Common Characters (counter & counter) 1122.py Relative Sort Array (counter, sort) 1169.py Invalid Transactions (permutations) 1170.py Compare Strings by Frequency of the Smallest Character (minmal counting) 1172.py Dinner Plate Stacks (heap, responsibilities) 1224.py Maximum Equal Frequency 1239.py Maximum Length of a Concatenated String with Unique Characters (set operation) 1247.py Minimum Swaps to Make Strings Equal (meaning of swap) 1260.py Shift 2D Grid (serialize and shift) 5181.py Distance Between Bus Stops 5222.py Split a String in Balanced Strings
Sort	Sorting.py 15.py 3Sum (two pointers) 41.py First Missing Positive 49.py Group Anagrams 56.py Merge Intervals (lambda sort key) 75.py Sort Colors 220.py Contains Duplicate III 253.py Meeting Rooms II 295.py Find Median from Data Stream 539.py Minimum Time Difference 953.py Verifying an Alien Dictionary 1051.py Height Checker
Tree	Traversal.py / BinarySearchTree.py / BinaryTreeProperty.py 98.py Validate Binary Search Tree (DFS min,max propagation) 102.py Binary Tree Level Order Traversal (BFS level propagation) 104.py Maximum Depth of Binary Tree (BFS level propagation) 105.py Construct Binary Tree from Preorder and Inorder Traversal (DFS .index and slice) 108.py Convert Sorted Array to Binary Search Tree (DFS mid and slice) 226.py Invert Binary Tree (DFS/BFS traversal) 250.py Count Univalue Subtrees (BFS&DFS check each subtrees) 333.py Largest BST Subtree (BFS&DFS check each subtrees, size in DFS/root in BFS) 863.py All Nodes Distance K in Binary Tree (DFS annotate parent, BFS condition traversal)
Graph	Graph.py 200.py Number of Islands 1222.py Queens That Can Attack the King
LinkedList	19.py Remove Nth Node From End of List 141.py Linked List Cycle (slow/fast pointers) 206.py Reverse Linked List (prev/curr pointers) 160.py Intersection of Two Linked Lists 1171.py Remove Zero Sum Consecutive Nodes from Linked List
Dynamic Programming	55.py Jump Game 62.py Unique Paths 70.py Climbing Stairs 72.py Edit Distance 1223.py Dice Roll Simulation
Sub Array Sub String	53.py Maximum Subarray (add or new subsum) 121.py Best Time to Buy and Sell Stock (just cares last) 152.py Maximum Product Subarray (min * negative) 386.py Longest Substring with At Most K Distinct Characters (just cares last, idx-left+1) 1233.py Remove Sub-Folders from the Filesystem (rfind, set lookup) 1248.py Count Number of Nice Subarrays (atMost(k)-atMost(k - 1))
Binary Search	BinarySearchVariants.py 33.py Search in Rotated Sorted Array (check sorted part) 1237.py Find Positive Integer Solution for a Given Equation (search in constraint range)
Math	The Aggregate Magic Algorithms 1.py Two Sum 7.py Reverse Integer (while != 0) 172.py Factorial Trailing Zeroes (while != 0) 224.py Basic Calculator 1071.py Greatest Common Divisor of Strings (GCD(b, a%b)) 1232.py Check If It Is a Straight Line (dx1dy2=dy1dx2) 1238.py Circular Permutation in Binary Representation (gray code x ^ x>>1) 1262.py Greatest Sum Divisible by Three (modulo removal) 5183.py Day of the Week

Bash

• Bash Reference Manual: link

Title	Solution
Bash Builtin	builtin.sh
Array	Array.sh
Find Command	find.sh

Language

Title	Solution
MRO	MRO.py (MAGIC MRO!) MainClazz.java (NO MRO) Main.cpp (NO MRO)