statistics.md

Arrays

• easy:

  • Longest Continuous Increasing Subsequence
  • Find All Numbers Disappeared in an Array
  • Shortest Unsorted Continuous Subarray
  • Third Maximum Number
  • Non-decreasing Array
  • Array Partition I
  • Flipping an Image
  • Transpose Matrix
  • Missing Number
  • Rotate Array
  • 3Sum

• medium:

  • Minimum Increment to Make Array Unique
  • Find all Duplicates in an Array
  • Product Of Array Except Self
  • Sum of Subarray Minimums
  • Minimum Path Sum
  • Teemo Attacking
  • Rotate Image
  • Word Search

• hard:

  • Find Minimum in Rotated Sorted Array II
  • Median of Two Sorted Arrays
  • First Missing Positive
  • Jump Game II

Dynamic programming

• easy:

  • Best Time to Buy and Sell Stock
  • Min Cost Climbing Stairs
  • Maximum Subarray

• medium:

  • Best Time to Buy and Sell Stock with Cooldown
  • Count Numbers with Unique Digits
  • Longest Increasing Subsequence
  • Longest Palindromic Substring
  • Range Sum Query 2D - Immutable
  • Longest Arithmetic Sequence
  • Partition Equal Subset Sum
  • Minimum Falling Path Sum
  • Minimum Cost For Tickets
  • Maximum Product Subarray
  • Palindromic Substrings
  • Out of Boundary Paths
  • Arithmetic Slices
  • Keys Key board
  • Maximal Square
  • Integer Break
  • Unique Paths
  • Decode Ways
  • Coin Change
  • Word Break
  • Target Sum
  • Can I Win

• hard:

  • Best Time to Buy and Sell Stock IV
  • Regular Expression Matching
  • Palindrome Partitioning II
  • Smallest Sufficient Team
  • Wildcard Matching
  • Decode Ways II
  • Edit Distance
  • Odd Even Jump

String

• easy:

  • Longest Common Prefix
  • Judge Route Circle
  • Long Pressed Name
  • Reverse String
  • To Lower Case

• medium:

  • Find and Replace Pattern
  • Valid Parenthesis String
  • Generate Parentheses
  • Basic Calculator II
  • Custom Sort String
  • Group Anagrams

• hard:

  • Shortest Palindrome
  • Interleaving String
  • Palindrome Pairs

Math

• easy:

  • Excel Sheet Column Number
  • Self Dividing Numbers
  • Smallest Range I
  • Add Digits

• medium:

  • Encode And Decode Tiny URL
  • Reordered Power Of 2
  • Maximum Swap

• hard:

  • Split Array With Same Average
  • Basic Calculator

Tree

• easy:

  • Lowest Common Ancestor of a Binary Search Tree
  • Find Mode in Binary Search Tree
  • Minimum Depth of Binary Tree
  • Convert BST to Greater Tree
  • Maximum Depth Of N Tree
  • Diameter of Binary Tree
  • Merge Two Binary Trees
  • Leaf Similar Trees
  • Invert Binary Tree
  • Path Sum III
  • Path Sum

• medium:

  • Construct Binary Tree from Preorder and Inorder Traversal
  • Populating Next Right Pointers in Each Node II
  • Lowest Common Ancestor of a Binary Tree
  • All Nodes Distance K in Binary Tree
  • Flatten Binary Tree to Linked List
  • All Possible Full Binary Trees
  • Validate Binary Search Tree
  • Count Complete Tree Nodes
  • Maximum Binary Tree
  • Binary Tree Pruning

• hard:

  • SerializeAndDeserializeBinaryTree
  • Binary Tree Maximum Path Sum
  • Recover Binary Search Tree
  • Redundant Connection II
  • Binary Tree Cameras

Hash Table

• easy:

  • Uncommon Words From Two Sentences
  • Longest Harmonious Subsequence
  • Longest Palindrome
  • Jewels And Stones
  • Single Number
  • Two Sum

• medium:

  • Find All Anagrams in a String
  • Sort Characters By Frequency
  • Most Frequent Subtree Sum
  • Subarray Sum Equals K
  • Daily Temperatures

• hard:

  • Insert Delete Get Random Duplicates Allowed
  • Random Pick With Blacklist
  • Maximal Rectangle

Depth-first Search

• easy:

  • Convert Sorted Array to Binary Search Tree
  • Maximum Depth Of Binary Tree
  • Balanced Binary Tree
  • Employee Importance
  • Max Area of Island
  • Binary Tree Paths

• medium:

  • Find Largest Value in Each Tree Row
  • Find Bottom Left Tree Value
  • Matchsticks to Square
  • Surrounded Regions
  • Keys and Rooms
  • 01 Matrix

• hard:

  • Longest Increasing Path in a Matrix
  • Similar String Groups
  • Concatenated Words

Binary Search

• easy:

  • Two Sum Input Array is Sorted
  • Intersection of Two Arrays II
  • Search Insert Position

• medium:

  • Find First and Last Position of Element in Sorted Array
  • Kth Smallest Element in a Sorted Matrix
  • Capacity To Ship Packages Within D Days
  • Search in Rotated Sorted Array II
  • Search in Rotated Sorted Array
  • Kth Smallest Element in a BST
  • Time Based Key-Value Store
  • 4Sum II

• hard:

  • Kth Smallest Number in Multiplication Table
  • Max Sum of Rectangle no Larger Than K
  • Russian Doll Envelopes
  • Swim In Rising Water
  • Three Equal Parts
  • Dungeon Game

Two Points

• easy:

  • Intersection of Two Arrays
  • Backspace String Compare
  • Move Zeroes

• medium:

  • Longest Word in Dictionary Through Deleting
  • Find the Duplicate Number
  • Container With Most Water
  • Partition Labels

• hard:

  • Trapping Rain Water

Breadth-first Search

• easy:

  • Binary Tree Level Order Traversal II
  • N-ary Tree Level Order Traversal
  • Symmetric Tree

• medium:

  • Binary Tree Level Order Traversal
  • Binary Tree Right Side View
  • Perfect Squares
  • Open The Lock

• hard:

  • Shortest Path To Get All Keys
  • Cut Off Trees For Golf Event
  • Escape a Large Maze
  • KSimilar Strings
  • Sliding Puzzle

Stack

• easy:

  • Remove All Adjacent Duplicates In String
  • Implement Queue Using Stacks
  • Valid Parentheses
  • Min Stack

• medium:

  • Binary Tree Zigzag Level Order Traversal
  • Next Greater Node In Linked List
  • Binary Tree Preorder Traversal
  • Binary Tree Inorder Traversal
  • Validate Stack Sequences
  • Next Greater Element II
  • Decoded String at Index
  • Online Stock Span
  • Decode String
  • 132 Pattern

• hard:

  • Binary Tree Postorder Traversal
  • Largest Rectangle in Histogram
  • Maximum Frequency Stack
  • Number of Atoms

Backtracking

• easy:

  • Letter Case Permutation

• medium:

  • Letter Combinations of a Phone Number
  • Palindrome Partitioning
  • Beautiful Arrangement
  • Combination Sum III
  • Combination Sum
  • Permutations

• hard:

  • Word Search II
  • Word Break II
  • Sudoku Solver

Design

• easy:

  • Design Linked List
  • Design HashMap
  • Design HashSet

• medium:

  • Flatten Nested List Iterator
  • Binary Search Tree Iterator
  • Design Circular Deque
  • Design Twitter

• hard:

  • All O'One Data Structure
  • LRU Cache
  • LFU Cache

Greedy

• easy:

  • Maximize Sum Of Array After K Negations
  • Split a String in Balanced Strings
  • Two City Scheduling
  • Lemonade Change
  • Assign Cookies

• medium:

  • Minimum Number of Arrows to Burst Balloons
  • Minimum Add to Make Parentheses Valid
  • Delete Columns to Make Sorted II
  • Score After Flipping Matrix
  • Is Subsequence
  • Task Scheduler
  • Gas Station
  • Jump Game

• hard:

  • Couples Holding Hands
  • Candy
  • IPO

Linked List

• easy:

  • Intersection of Two Linked Lists
  • Middle of the Linked List
  • Merge Two Sorted Lists
  • Palindrome Linked List
  • Reverse Linked List
  • Linked List Cycle

• medium:

  • Remove Nth Node From End of List
  • Copy List with Random Pointer
  • Split Linked List in Parts
  • Add Two Numbers
  • Linked List Cycle II
  • Odd Even Linked List
  • Add Two Numbers II

• hard:

  • Reverse Nodes in K-Group
  • Merge K Sorted Lists

Bit Manipulation

• easy:

  • Binary Number with Alternating Bits
  • Number Complement
  • Hamming Distance

• medium:

  • Total Hamming Distance
  • Single Number III
  • Subsets

Heap

• easy:

  • Kth Largest Element in a Stream

• medium:

  • Kth Largest Element in an Array
  • Cheapest Flights Within K Stops
  • Top K Frequent Elements
  • Top K Frequent Words

• hard:

  • Minimum Number of Refueling Stops
  • Find Median From Data Stream
  • The Skyline Problem

Sort

• easy:

  • Valid Anagram

• medium:

  • Reorganize String
  • Merge Intervals
  • Sort Colors
  • Sort List

• hard:

  • Insert Interval
  • Maximum Gap

Graph

• easy:

  • Find the Town Judge

• medium:

  • Satisfiability of Equality Equations
  • Find Eventual Safe States
  • Reconstruct Itinerary
  • Redundant Connection
  • Minimum Height Trees
  • Is Graph Bipartite
  • Evaluate Division
  • Clone Graph

Divide and Conquer

• easy:

  • Majority Element

• medium:

  • Different Ways to Add Parentheses
  • Search a 2D Matrix II

• hard:

  • Count of Smaller Numbers After Self
  • Expression Add Operators

Union Find

• medium:

  • Number of Islands
  • Friend Circles
  • Accounts Merge

• hard:

  • Largest Component Size by Common Factor
  • Longest Consecutive Sequence

Trie

• medium:

  • Implement Trie (Prefix Tree)
  • Implement Magic Dictionary
  • Map Sum Pairs
  • Replace Words

• hard:

  • Prefix and Suffix Search

Binary Search Tree

• easy:

  • Minimum Distance Between BST Nodes
  • Minimum Absolute Difference in BST

• medium:

  • Contains Duplicate III

• hard:

  • Data Stream as Disjoint Intervals
  • Falling Squares
  • My Calendar III

Recursion

• easy:

  • Longest Univalue Path

• medium:

  • Partition to K Equal Sum Subsets
  • K-th Symbol in Grammar

Segment Tree

• medium:

  • Range Sum Query Mutable

• hard:

  • Rectangle Area II

Queue

• medium:
  • Design Circular Queue

Random

• medium:
  • Implement Rand10 Using Rand7
  • Random Pick with Weight

Topological Sort

• medium:
  • Course Schedule II
  • Course Schedule

Reservoir Sampling

• medium:
  • Linked List Random Node

Map

• medium:
  • Hand of Straights

Sliding Window

• medium:

  • Longest Substring Without Repeating Characters

• hard:

  • Sliding Window Maximum

Concurrency

• easy:

  • Print in Order

• medium:

  • Print FooBar Alternately
  • Print Zero Even Odd
  • Building H2O

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