DSA PROBLEMS

Problems pattern frequency

Conditional: 9

Loop: 15

Pattern printing: 15

STL: 9

Basic math: 15

Base conversion: 9

Binary search: 18

Sorting: 15

Greedy: 12

Divide and conquer: 6

Algorithm: 30

Searching: 12

Recursion: 30

Backtracking: 15

String matching: 9

Simulation: 9

Bitmask: 12

Combinatorics: 12

Line sweep: 9

Dynamic programming: 50

Array: 60

String: 50

Matrix: 45

Linked list: 30

Tree: 45

Binary tree: 30

Binary search tree: 18

Graph: 50

Hash table: 21

Stack: 15

Queue: 12

Heap: 18

Trie: 9

Segment tree: 9

Two pointers: 18

Sliding window: 15

Prefix sum: 9

Cyclic sort: 9

Monotonic stack: 9

Monotonic queue: 6

Tree view: 6

Advance tree traversal: 6

Tree construction: 6

Top k element: 3

K way merge: 3

Two heaps: 6

Fast & slow pointers: 6

In-place reversal: 6

0/409

Solved

Easy

0/103

Med.

0/238

Hard

0/60

Expert

0/8

Revision

Difficulty

Status

Topics

Problem	Tags	Difficulty
Number is Positive or Negative	Math Conditional Comparison	Easy
Largest among three numbers	Math Conditional Comparison	Easy
Grading Scale System	Conditional Comparison	Easy
Ternary Operator (Even Odd)	Math Conditional	Easy
Leap Year	Math Conditional	Easy
Simple Calculator	Math Conditional Operators	Easy
Traffic Light System	Conditional Simulation	Easy
Number of Days in a Month	Math Conditional	Easy
Print numbers from 1 to n	Loop Iteration	Easy
Sum of n natural numbers	Loop Math Summation	Easy
Factorial of a number	Loop Math Recursion	Medium
Print multiplication table	Loop Math Multiplication	Easy
Skip numbers divisible by 3 or 5	Loop Conditional	Medium
Fibonacci Sequence	Loop Recursion Math	Medium
Solid Square	Loop Pattern Printing	Easy
Hollow Square	Loop Pattern Printing	Easy
Right Angled Triangle	Loop Pattern Printing	Easy
Inverted Right Angled Triangle	Loop Pattern Printing	Easy
Left Angled Triangle	Loop Pattern Printing	Easy
Inverted Left Angled Triangle	Loop Pattern Printing	Easy
Full Pyramid	Loop Pattern Printing	Easy
Inverted Full Pyramid	Loop Pattern Printing	Easy
Pascal's Triangle	Loop Pattern Printing Math	Medium
Diamond	Loop Pattern Printing	Medium
Butterfly	Loop Pattern Printing	Medium
Sandglass	Loop Pattern Printing	Medium
Heart Shape	Loop Pattern Printing	Medium
Concentric Squares	Loop Pattern Printing	Medium
Big Temple	Loop Pattern Printing	Medium
Pair	STL Data Structures Utility	Easy
Vector	STL Data Structures Dynamic Array	Easy
String	STL Data Structures Text Processing	Easy
Map	STL Data Structures Associative Container	Medium
Unordered Map	STL Data Structures Associative Container	Medium
Set	STL Data Structures Ordered Set	Easy
Unordered Set	STL Data Structures Hashing	Medium
Stack	STL Data Structures LIFO	Easy
Queue	STL Data Structures FIFO	Easy
Priority Queue	STL Data Structures Heap	Medium
Count Number of Digits	Basic Math Number Digit Recursion	Easy
Sum of Digits	Basic Math Number Digit Recursion	Easy
Product of Digits	Basic Math Number Digit Recursion	Medium
Reverse a Number	Basic Math Number Digit Recursion	Easy
Palindrome Number	Basic Math Number Digit Recursion	Medium
Smallest and Largest Digits	Basic Math Number Digit	Easy
Remove Digits from Number	Basic Math Number Digit	Medium
Replace Digit with Another Digit	Basic Math Number Digit	Medium
Difference of Sum of Even and Odd Digits	Basic Math Number Digit	Medium
Armstrong Number	Basic Math Number Digit	Easy
Perfect Number	Basic Math Number Digit	Easy
Given Number is Prime or Not	Basic Math Prime Number	Easy
Print All Prime Numbers in a Range	Basic Math Prime Number Loop Recursion	Medium
Count All Prime Numbers in Given Range	Basic Math Prime Number Loop Recursion	Medium
Prime Factors	Basic Math Prime Number Factorization	Medium
Largest Prime Factor	Basic Math Prime Number Factorization	Hard
Nth Prime Number in a Range	Basic Math Prime Number Loop	Hard
Euclidean Algorithm	Basic Math Algorithm Number Theory Recursion	Medium
Sieve of Eratosthenes	Basic Math Algorithm Prime Number	Hard
Binary Exponentiation	Basic Math Algorithm Exponentiation	Hard
Decimal to Binary	Base Conversion Binary Number System Recursion	Easy
Binary to Decimal	Base Conversion Binary Number System	Easy
Decimal to Octal	Base Conversion Octal Number System	Easy
Decimal to Hexadecimal	Base Conversion Hexadecimal Number System	Medium
Decimal to Given Base	Base Conversion Number System Mathematics	Medium
Binary to Gray Code	Base Conversion Gray Code Binary	Medium
Gray Code to Binary	Base Conversion Gray Code Binary	Medium
Octal to Hexadecimal	Base Conversion Octal Hexadecimal	Medium
Hexadecimal to Binary	Base Conversion Hexadecimal Binary	Medium
Second Largest Element in Array	Array Sorting Brute Force	Easy
Left Rotate Array by K Places	Array Rotation Two Pointers	Medium
Merge Two Sorted Arrays	Array Sorting Merge Recursion	Medium
Missing Number in Array	Array Mathematics Bit Manipulation	Easy
Find the Duplicate Number	Array Cycle Detection Two Pointers	Medium
Two Sum	Array Hash Table Two Pointers	Easy
Missing and Repeating Number	Array Mathematics Sorting	Medium
Next Permutation	Array Greedy Sorting	Medium
Remove Duplicates from Sorted Array	Array Two Pointers	Easy
Diagonal Sum	Matrix Mathematics Summation	Easy
Sum of Upper and Lower Triangle	Matrix Mathematics Summation	Medium
Transpose of Matrix	Matrix Mathematics Transformation	Easy
Spiral Matrix	Matrix Simulation Traversal	Medium
Spiral Matrix II	Matrix Simulation Traversal	Medium
Boundary Traversal of Matrix	Matrix Traversal	Easy
Set Matrix Zeroes	Matrix Array In-Place Modification	Medium
Rotate Image	Matrix Transformation In-Place Modification	Medium
Row with Maximum Ones	Matrix Binary Search	Easy
Count of Lower and Upper Characters	String Character Analysis Recursion	Easy
Palindrome String	String Two Pointers Recursion	Easy
Reverse String	String Recursion	Easy
Isomorphic String	String Hash Map	Medium
Longest Common Prefix	String Sorting	Medium
Roman Number to Integer	String Mathematics	Medium
Implement Atoi	String Parsing	Medium
Anagram of String	String Sorting	Easy
Sum of Two Largest Numbers	String Sorting Mathematics	Medium
Selection Sort	Sorting Brute Force Array	Easy
Bubble Sort	Sorting Brute Force Array	Easy
Insertion Sort	Sorting Recursion Array	Easy
Merge Sort	Sorting Recursion Divide and Conquer	Medium
Quick Sort	Sorting Recursion Divide and Conquer	Medium
Counting Sort	Sorting Non-Comparison Sort Array	Medium
Bottom-Up Merge Sort	Sorting Recursion Divide and Conquer	Medium
Hybrid Quick Sort	Sorting Recursion Divide and Conquer	Hard
Quick Sort using Dutch National Flag Algorithm	Sorting Partitioning Recursion	Hard
Linear Search	Searching Linear Search Brute Force	Easy
Binary Search	Searching Binary Search Recursion Divide and Conquer	Easy
Search Insert Position	Searching Binary Search Array	Easy
Sqrt(x)	Searching Binary Search Mathematics	Medium
Find First and Last Position of Element in Sorted Array	Searching Binary Search Array	Medium
Valid Perfect Square	Searching Binary Search Mathematics	Easy
Search in Rotated Sorted Array	Searching Binary Search Array	Medium
Search in Rotated Sorted Array II	Searching Binary Search Array	Medium
Find Minimum in Rotated Sorted Array	Searching Binary Search Array	Medium
Find Minimum in Rotated Sorted Array II	Searching Binary Search Array	Medium
Find Peak Element	Searching Binary Search Array	Medium
Median of Two Sorted Arrays	Searching Binary Search Divide and Conquer	Hard
Find in Mountain Array	Searching Binary Search Array	Hard
Allocate Minimum Pages	Searching Binary Search Array	Hard
Painters Partition Problem	Searching Binary Search Array	Hard
Capacity to Ship Packages Within D Days	Searching Binary Search Greedy	Hard
Aggressive Cows	Searching Binary Search Greedy	Hard
Koko Eating Bananas	Searching Binary Search Greedy	Hard
Magnetic Force Between Two Balls	Searching Binary Search Greedy	Hard
Search a 2D Matrix	Searching Binary Search Matrix Array	Medium
Search a 2D Matrix II	Searching Binary Search Matrix Divide and Conquer	Medium
Search in a Row-Column Sorted Array	Searching Binary Search Matrix Greedy	Medium
Kth Smallest Element in a Sorted Matrix	Searching Binary Search Matrix Heap	Hard
Exponential Search	Searching Exponential Search Binary Search Recursion	Medium
Kadane's Algorithm	Array Algorithm Dynamic Programming	Medium
Maximum Subarray	Array Algorithm Dynamic Programming	Medium
Largest Sum Contiguous Subarray	Array Algorithm Dynamic Programming	Medium
Dutch National Flag Algorithm	Array Algorithm Sorting	Medium
Sorting an Array Containing Only 0's, 1's, and 2's	Array Algorithm Sorting	Medium
Difference Between Ones and Zeros in Row and Column	Array Algorithm Matrix	Medium
Moore's Voting Algorithm	Array Algorithm Greedy	Medium
Majority Element	Array Algorithm Hash Map	Easy
Majority Element II	Array Algorithm Greedy	Medium
Minimum Index of a Valid Split	Array Algorithm Sorting	Medium
KMP Algorithm	String Algorithm Pattern Matching Recursion	Expert
Z Algorithm	String Algorithm Pattern Matching	Expert
Rabin-Karp Algorithm	String Algorithm Hashing	Expert
Remove Element	Array Two Pointers In-Place Modification	Easy
Two Sum II - Input Array Is Sorted	Array Two Pointers Binary Search	Medium
Three Sum	Array Two Pointers Sorting	Medium
Four Sum	Array Two Pointers Sorting	Medium
Container With Most Water	Array Two Pointers Greedy	Medium
Trapping Rain Water	Array Two Pointers Dynamic Programming	Hard
3Sum Smaller	Array Two Pointers Sorting	Medium
Valid Palindrome	String Two Pointers Recursion	Easy
Reverse Words in a String	String Two Pointers Sorting	Medium
Compare Version Numbers	String Two Pointers Sorting	Medium
Reverse Vowels of a String	String Two Pointers Recursion	Easy
Reverse Only Letters	String Two Pointers Sorting	Easy
One Edit Distance	String Two Pointers Dynamic Programming	Medium
Contains Duplicate II	Array Sliding Window Hash Table	Easy
Minimum Size Subarray Sum	Array Sliding Window Binary Search	Medium
Maximum Product Subarray	Array Sliding Window Dynamic Programming	Medium
Fruit Into Baskets	Array Sliding Window	Medium
Count the Number of Good Subarrays	Array Sliding Window Recursion	Hard
Minimum Swaps to Group All 1's Together	Array Sliding Window	Medium
Longest Substring Without Repeating Characters	String Sliding Window Hash Table	Medium
Minimum Window Substring	String Sliding Window Hash Table	Hard
Permutation in String	String Sliding Window Recursion	Medium
Find All Anagrams in a String	String Sliding Window Hash Table	Medium
Number of Substrings Containing All Three Characters	String Sliding Window	Medium
Longest Substring with At Most Two Distinct Characters	String Sliding Window	Medium
Substring with Concatenation of All Words	String Sliding Window Recursion	Hard
Longest Substring with At Most K Distinct Characters	String Sliding Window	Medium
Longest K Unique Characters Substring	String Sliding Window	Medium
Product of Array Except Self	Array Prefix Sum Math	Medium
Continuous Subarray Sum	Array Prefix Sum Hash Table	Medium
Subarray Sum Equals K	Array Prefix Sum Recursion Hash Table	Medium
Binary Subarray With Sum	Array Prefix Sum Sliding Window	Medium
Range Sum Query - Immutable	Array Prefix Sum Dynamic Programming	Easy
Find the Middle Index in Array	Array Prefix Sum	Easy
Subarray Sum Equals K	Array Prefix Sum Recursion Hash Table	Medium
Range Addition	Array Prefix Sum Difference Array	Medium
Maximum Size Subarray Sum Equals K	Array Prefix Sum Hash Table Recursion	Medium
Cyclic Sort	Array Cyclic Sort	Easy
Missing Number	Array Cyclic Sort Math	Easy
Find All Numbers Disappeared in an Array	Array Cyclic Sort	Medium
Set Mismatch	Array Cyclic Sort	Easy
Find All Duplicates in an Array	Array Cyclic Sort	Medium
Find the First K Missing Positive Numbers	Array Cyclic Sort Heap Recursion	Medium
Floor and Ceil of a Number in Sorted Array	Divide and Conquer Binary Search Array	Medium
Smallest Missing Number in Sorted Array	Divide and Conquer Binary Search Array	Medium
Power Function Using Divide and Conquer	Divide and Conquer Recursion Math	Medium
Permutations	Backtracking Array Recursion	Medium
Permutations II	Backtracking Array Recursion	Medium
Subsets	Backtracking Array Recursion	Medium
Subsets II	Backtracking Array Recursion	Medium
Combinations	Backtracking Array Recursion	Medium
Combination Sum	Backtracking Array Recursion	Medium
Combination Sum II	Backtracking Array Recursion	Medium
Combination Sum III	Backtracking Array Recursion	Medium
Rat in a Maze	Backtracking Array Recursion	Medium
N-Queens	Backtracking Array Recursion	Hard
N-Queens II	Backtracking Array Recursion	Hard
Sudoku Solver	Backtracking Array Recursion	Hard
Permutations of a String	Backtracking String Recursion	Medium
Combinations of a String	Backtracking String Recursion	Medium
Letter Combinations of a Phone Number	Backtracking String Recursion	Medium
Word Search	Backtracking String Recursion Matrix	Medium
Word Search II	Backtracking String Recursion Trie Matrix	Hard
Restore IP Addresses	Backtracking String Recursion	Medium
Expression Add Operators	Backtracking String Recursion Math	Hard
Letter Case Permutation	Backtracking String Recursion	Medium
Word Squares	Backtracking String Recursion Trie	Hard
Design HashMap	Hashing Design Array	Medium
Contains Duplicate II	Hashing Array Sliding Window	Easy
Group Anagrams	Hashing String Sorting	Medium
Jewels and Stones	Hashing String	Easy
Frequency Tracker	Hashing Array Recursion	Medium
Count Elements with Maximum Frequency	Hashing Array	Medium
Delete in a Singly Linked List	Linked List	Easy
Remove Every Kth Node	Linked List	Medium
Remove Nth Node from End of List	Linked List Two Pointers	Medium
Swapping Nodes in a Linked List	Linked List Two Pointers	Medium
Swap Nodes in Pairs	Linked List Recursion	Medium
Merge Two Sorted Lists	Linked List Recursion	Easy
Merge K Sorted Lists	Linked List Heap Recursion Divide and Conquer	Hard
Swap Nodes in Pairs II	Linked List Recursion	Medium
Cycle in Linked List	Fast & Slow Pointers Linked List	Easy
Middle of the Linked List	Fast & Slow Pointers Linked List	Easy
Length of Cycle in Linked List	Fast & Slow Pointers Linked List	Medium
Starting Node of Cycle in Linked List	Fast & Slow Pointers Linked List	Medium
Palindrome Linked List	Fast & Slow Pointers In-Place Reversal Linked List Recursion	Medium
Delete the Middle Node of a Linked List	Fast & Slow Pointers Linked List	Medium
Odd Even Linked List	Fast & Slow Pointers Linked List	Medium
Reverse Linked List	In-Place Reversal Linked List Recursion	Easy
Reverse Linked List II	In-Place Reversal Linked List	Medium
Reverse Doubly Linked List	In-Place Reversal Linked List	Medium
Reverse Nodes in Even Length Groups	In-Place Reversal Linked List	Medium
Reverse Nodes in K-Group	In-Place Reversal Linked List Recursion	Hard
Print Immutable Linked List in Reverse	In-Place Reversal Linked List Recursion	Medium
Rotate List	In-Place Reversal Linked List	Medium
Reorder List	In-Place Reversal Linked List	Medium
Partition List	In-Place Reversal Linked List	Medium
Odd Even Linked List	In-Place Reversal Linked List	Medium
Add Two Numbers	Linked List Math	Medium
Add Two Numbers II	Linked List Stack	Medium
Sort a Linked List of 0s, 1s, and 2s	Linked List Sorting	Medium
Insertion Sort Linked List	Linked List Sorting	Medium
Sort List	Linked List Sorting Merge Sort	Medium
Quick Sort in Linked List	Linked List Sorting Recursion Quick Sort	Hard
Flatten a Linked List	Linked List Recursion	Medium
Clone a Linked List with Next and Random Pointer	Linked List Hashing	Medium
Implement Stack Using Array	Stack Array	Easy
Implement Stack Using Linked List	Stack Linked List	Easy
Valid Parentheses	Stack String	Easy
Longest Valid Parentheses	Stack String Dynamic Programming	Hard
Basic Calculator	Stack String Recursion	Hard
Reverse a Stack	Stack Recursion	Medium
Sort a Stack	Stack Sorting Recursion	Medium
Implement Two Stacks in an Array	Stack Array	Medium
The Celebrity Problem	Stack Matrix	Medium
N Stacks in an Array	Stack Array	Hard
Next Greater Element I	Stack Monotonic Stack Array	Easy
Next Greater Element II	Stack Monotonic Stack Array	Medium
Help Classmates (Next Smaller Number)	Stack Monotonic Stack Array	Medium
Previous Greater Element	Stack Monotonic Stack Array	Medium
Previous Smaller Element	Stack Monotonic Stack Array	Medium
Remove K Digits	Stack Monotonic Stack Greedy	Medium
Daily Temperatures	Stack Monotonic Stack Array	Medium
Online Stock Span	Stack Monotonic Stack	Medium
Remove Duplicate Letters	Stack Monotonic Stack Greedy	Hard
Largest Rectangle in Histogram	Stack Monotonic Stack Array	Hard
Maximal Rectangle	Stack Monotonic Stack Matrix	Hard
Next Greater Node in Linked List	Stack Monotonic Stack Linked List	Medium
Infix to Postfix	Stack Notation Conversions	Medium
Infix to Prefix	Stack Notation Conversions	Medium
Prefix to Postfix	Stack Notation Conversions	Medium
Prefix to Infix	Stack Notation Conversions	Medium
Postfix to Infix	Stack Notation Conversions	Medium
Postfix to Prefix	Stack Notation Conversions	Medium
Implement Queue Using Array	Queue Array	Easy
Implement Queue Using Linked List	Queue Linked List	Easy
Reverse First K Elements of Queue	Queue Stack Recursion	Medium
Implement Circular Queue	Queue Array	Medium
Implement Stack Using Queue	Queue Stack	Medium
Implement Queue Using Stack	Queue Stack	Medium
Implement Deque	Queue Deque	Medium
Sliding Window Maximum	Queue Monotonic Queue Deque	Hard
Queue Reconstruction by Height	Queue Sorting	Medium
Shortest Subarray with Sum at Least K	Queue Monotonic Queue Sliding Window	Hard
Sum of Subarray Minimums	Queue Monotonic Queue Stack	Medium
Sentence Similarity III	Queue String	Medium
Design a Stack with O(1) Push, Pop, and Min Operations	Queue Stack Monotonic Stack	Medium
Continuous Subarrays	Queue Monotonic Queue Sliding Window	Medium
Level Order Traversal	Tree Binary Tree Queue	Medium
Inorder Traversal	Tree Binary Tree Recursion Stack	Easy
Preorder Traversal	Tree Binary Tree Recursion Stack	Easy
Postorder Traversal	Tree Binary Tree Recursion Stack	Easy
Maximum Depth of Binary Tree	Tree Binary Tree Recursion	Easy
Minimum Depth of Binary Tree	Tree Binary Tree Recursion	Easy
Diameter of Tree	Tree Binary Tree Recursion	Medium
Same Tree	Tree Binary Tree Recursion	Easy
Symmetric Tree	Tree Binary Tree Recursion	Easy
Balanced Binary Tree	Tree Binary Tree Recursion	Easy
Merge Two Binary Trees	Tree Binary Tree Recursion	Easy
Invert Binary Tree	Tree Binary Tree Recursion	Easy
Insert a Node in a BST	Tree Binary Search Tree Recursion	Medium
Search a Node in BST	Tree Binary Search Tree Recursion	Easy
Delete a Node from BST	Tree Binary Search Tree Recursion	Medium
Check for BST	Tree Binary Search Tree Recursion	Medium
Kth Largest Element in BST	Tree Binary Search Tree Recursion	Medium
Kth Smallest Element in BST	Tree Binary Search Tree Recursion	Medium
Validate Binary Search Tree	Tree Binary Search Tree Recursion	Medium
All Elements in Two Binary Search Trees	Tree Binary Search Tree Sorting	Medium
Trim a Binary Search Tree	Tree Binary Search Tree Recursion	Medium
Left View of Binary Tree	Tree Tree View Recursion Queue	Medium
Right View of Binary Tree	Tree Tree View Recursion Queue	Medium
Top View of Binary Tree	Tree Tree View Queue	Medium
Bottom View of Binary Tree	Tree Tree View Queue	Medium
Populating Next Right Pointers in Each Node	Tree Tree View Recursion Queue	Medium
Populating Next Right Pointers in Each Node II	Tree Tree View Recursion Queue	Medium
Zigzag Traversal	Tree Advanced Tree Traversal Queue	Medium
Boundary Traversal	Tree Advanced Tree Traversal Recursion	Medium
Vertical Order Traversal	Tree Advanced Tree Traversal Queue	Hard
Reverse Level Order Traversal	Tree Advanced Tree Traversal Queue	Medium
Diagonal Traversal	Tree Advanced Tree Traversal Queue	Medium
Spiral Traversal	Tree Advanced Tree Traversal Queue	Medium
Construct Binary Tree From Inorder & Preorder Traversal	Tree Tree Construction Recursion	Medium
Construct Binary Tree From Inorder & Postorder Traversal	Tree Tree Construction Recursion	Medium
Construct Binary Tree From Inorder & Level Order Traversal	Tree Tree Construction Recursion	Hard
Construct Binary Search Tree From Preorder Traversal	Tree Tree Construction Binary Search Tree Recursion	Medium
Construct Binary Search Tree From Postorder Traversal	Tree Tree Construction Binary Search Tree Recursion	Medium
Construct Binary Search Tree From Level Order Traversal	Tree Tree Construction Binary Search Tree Recursion	Hard
Morris Traversal for Inorder, Preorder, and Postorder	Tree Traversal Recursion	Hard
Lowest Common Ancestor of a Binary Tree	Tree Recursion	Medium
Lowest Common Ancestor of a Binary Search Tree	Tree Binary Search Tree Recursion	Easy
Lowest Common Ancestor of Deepest Leaves	Tree Recursion	Medium
Serialize and Deserialize Binary Tree	Tree Recursion String	Hard
All Nodes Distance K in Binary Tree	Tree Recursion Graph	Medium
Amount of Time for Binary Tree to Be Infected	Tree Recursion Graph	Medium
Flatten Binary Tree to Linked List	Tree Recursion Linked List	Medium
Inorder Successor in BST	Tree Binary Search Tree Recursion	Medium
Inorder Predecessor in BST	Tree Binary Search Tree Recursion	Medium
Split BST	Tree Binary Search Tree Recursion	Hard
Convert Binary Search Tree to Sorted Doubly Linked List	Tree Binary Search Tree Recursion Linked List	Hard
N-ary Tree Level Order Traversal	Tree N-ary Tree Queue	Medium
N-ary Tree Inorder Traversal	Tree N-ary Tree Recursion	Medium
N-ary Tree Preorder Traversal	Tree N-ary Tree Recursion	Easy
N-ary Tree Postorder Traversal	Tree N-ary Tree Recursion	Easy
Maximum Depth of N-ary Tree	Tree N-ary Tree Recursion	Easy
Diameter of N-ary Tree	Tree N-ary Tree Recursion	Medium
Clone N-ary Tree	Tree N-ary Tree Recursion	Medium
Serialize and Deserialize N-ary Tree	Tree N-ary Tree Recursion String	Hard
Encode N-ary Tree to Binary Tree	Tree N-ary Tree Binary Tree Recursion	Hard
Last Stone Weight	Heap Priority Queue Array	Easy
Take Gifts from the Richest Pile	Heap Priority Queue Array	Easy
Remove Stones to Minimize the Total	Heap Priority Queue Array	Medium
Maximum Spending After Buying Items	Heap Priority Queue Array	Medium
Number of Orders in the Backlog	Heap Priority Queue Array	Medium
Maximum Number of Points from Grid Queries	Heap Priority Queue Array	Hard
Maximum Number of Events That Can Be Attended	Heap Priority Queue Array	Hard
Meeting Rooms III	Heap Priority Queue Array	Expert
Zero Array Transformation III	Heap Priority Queue Array Recursion	Expert
First Unique Character in a String	Heap Priority Queue String	Easy
Reorganize String	Heap Priority Queue String	Medium
Find the Most Competitive Subsequence	Heap Priority Queue String	Medium
Length of the Longest Valid Substring	Heap Priority Queue String	Medium
Digit Operations to Make Two Integers Equal	Heap Priority Queue String	Hard
Get Biggest Three Rhombus Sums in a Grid	Heap Priority Queue String	Hard
Earliest Second to Mark Indices II	Heap Priority Queue String	Expert
Final Array State After K Multiplication Operations I	Heap Priority Queue String	Expert
Final Array State After K Multiplication Operations II	Heap Priority Queue String	Expert
Kth Largest Element in a Stream	Heap Priority Queue Top K Element	Easy
Find K Pairs with Smallest Sums	Heap Priority Queue Top K Element	Medium
Maximal Score After Applying K Operations	Heap Priority Queue Top K Element	Medium
Maximum Elegance of a K Length Subsequence	Heap Priority Queue Top K Element	Medium
Maximum Performance of a Team	Heap Priority Queue Top K Element	Hard
Maximum Subsequence Score	Heap Priority Queue Top K Element	Hard
Kth Largest Element in a Stream	Heap Priority Queue Top K Element	Easy
Find K Pairs with Smallest Sums	Heap Priority Queue Top K Element	Medium
Maximal Score After Applying K Operations	Heap Priority Queue Top K Element	Medium
IPO	Heap Priority Queue Two Heap	Hard
Find Median From Data Stream	Heap Priority Queue Two Heap Recursion	Hard
Find Right Interval	Heap Priority Queue Two Heap	Medium
Implement Trie (Prefix Tree)	Trie Recursion	Medium
Add and Search Word - Data Structure Design	Trie Recursion	Medium
Word Search II	Trie Recursion Backtracking	Hard
Replace Words	Trie Recursion String	Medium
Longest Word in Dictionary	Trie Recursion Sorting	Medium
Maximum XOR of Two Numbers in an Array	Trie Bit Manipulation	Hard
Smallest String Starting From Leaf	Trie Recursion Tree	Medium
Distinct Substrings of a String	Trie Recursion String	Hard
Longest Common Prefix	Trie Recursion String	Easy
Merge Interval	Interval Sorting	Medium
Count Days Without Meetings	Interval Sorting	Easy
Determine If Two Events Have Conflict	Interval Sorting	Easy
Insert Interval	Interval Sorting	Medium
Interval List Intersections	Interval Sorting Two Pointers	Medium
Remove Interval	Interval Sorting	Medium
Non-Overlapping Intervals	Interval Sorting Greedy	Medium
Minimum Interval to Include Each Query	Interval Sorting Heap Priority Queue	Hard
Divide Intervals into Minimum Number of Groups	Interval Sorting Greedy	Medium
The Number of the Smallest Unoccupied Chair	Interval Sorting Heap Priority Queue	Medium
Data Stream as Disjoint Intervals	Interval Sorting Binary Search	Hard
Falling Squares	Interval Sorting Segment Tree	Hard
Insert Delete GetRandom O(1)	Design Hashing	Medium
LRU Cache	Design Hashing Linked List Two Heap	Medium
LFU Cache	Design Hashing Linked List Two Heap	Hard
Design Browser History	Design Stack Linked List	Medium
Design HashSet	Design Hashing	Easy
Design HashMap	Design Hashing	Easy
Design Circular Deque	Design Queue Linked List	Medium
Design a Food Rating System	Design Sorting Heap	Medium
Design a Number Container System	Design Sorting Heap	Medium