AlgoLounge

Questions

AlgoTime Winter 2026

Week 15

Two Sum
arrayhash-map
easy
Valid Parentheses
stack
easy
Binary Search
arraybinary-search
easy
Climbing Stairs
dynamic-programming
easy
Longest Substring Without Repeating Characters
sliding-window
medium
Course Schedule II
graphtopological-sort
medium
Trapping Rain Water
two-pointers
hard
Merge k Sorted Lists
linked-list
hard

Week 14

Assign Cookies
greedy
easy
Lemonade Change
greedy
easy
Jump Game
greedy
medium
Best Time to Buy and Sell Stock II
greedy
medium
Minimum Number of Refueling Stops
greedyheap-priority-queue
hard

Week 13

Summary Ranges
intervals
easy
Meeting Rooms
intervals
easy
Merge Intervals
intervals
medium
Non-Overlapping Intervals
intervals
medium
Employee Free Time
intervals
hard

Week 12

First Unique Character in a String
string
easy
Longest Word in Dictionary
stringtrie
easy
Implement Trie (Prefix Tree)
trie
medium
Replace Words
trie
medium
Word Search II
tries
hard

Week 11

Valid Parentheses
stack
easy
Backspace String Compare
stack
easy
Baseball Game
medium
Evaluate Reverse Polish Notation
medium
Daily Temperatures
stack
medium
Decode String
stack
medium
Next Greater Element
stack
medium
Largest Rectangle In Histogram
stack
hard

Week 10

Binary Search
arraybinary-search
easy
Search a 2D Matrix
binary-search
medium
Find Minimum in Rotated Sorted Array
binary-search
medium
Search in Rotated Sorted Array
binary-search
medium
Koko Eating Bananas
binary-search
medium
Median of Two Sorted Arrays
binary-search
hard

Week 9

Best Time to Buy and Sell Stock
sliding-window
easy
Longest Substring Without Repeating Characters
sliding-window
medium
Longest Repeating Character Replacement
sliding-window
medium
Permutation In String
sliding-window
medium
Minimum Window Substring
sliding-window
hard
Sliding Window Maximum
sliding-window
hard

Week 8

Contains Duplicate
arrays-and-hashing
easy
Last Stone Weight
heap-priority-queue
easy
Kth Largest Element in a Stream
heap-priority-queue
easy
Meeting Rooms II
intervalsheap-priority-queue
medium
Design Twitter
heap-priority-queue
medium
Find Median From Data Stream
heap-priority-queue
hard

Week 7

Reverse Vowels of a String
stringtwo-pointers
easy
Move Zeroes
arrays-and-hashingtwo-pointers
easy
Find the Town Judge
graph
easy
Pacific Atlantic Water Flow
graphdfs
medium
Course Schedule II
graphtopological-sort
medium
Alien Dictionary
graphtopological-sort
hard
Swim in Rising Water
graphbfsheap-priority-queue
hard

Week 6

Single Number
bit-manipulation
easy
Climbing Stairs
dynamic-programming
easy
Min Cost Climbing Stairs
dynamic-programming
easy
House Robber
dynamic-programming
medium
Maximum Subarray
dynamic-programming
medium
Unique Paths
dynamic-programming
medium
Distinct Subsequences
dynamic-programming
hard

Week 5

Prototype Pattern
design-patterns
easy
Fibonacci Number
math
easy
Power of Two
math
easy
Pow(x, n)
math
medium
Subsets
backtracking
medium
Merge k Sorted Lists
linked-list
hard
Basic Calculator
stack
hard

Week 4

Adapter Pattern
design-patterns
easy
Same Tree
trees
easy
Subtree of Another Tree
trees
easy
Lowest Common Ancestor of a Binary Search Tree
trees
medium
Binary Tree Level Order Traversal
trees
medium
Binary Tree Maximum Path Sum
trees
hard

Week 3

Factory Method Pattern
design-patterns
easy
Design HashSet
hash-set
easy
Design HashMap
hash-map
easy
Repeated DNA Sequences
hash-mapsliding-window
medium
Fraction to Recurring Decimal
hash-map
medium
Sudoku Solver
backtracking
hard

Week 2

String Reversal
easy
Implement Linked List
linked-listdata-structure-design
easy
Palindrome Linked List
linked-listtwo-pointers
easy
Linked List Cycle Detection
linked-list
easy
Linked List Cycle II
linked-listtwo-pointers
medium
Remove Nth Node From End of List
linked-list
medium
Reverse Nodes in K-Group
linked-list
hard

Week 1

Two Sum
arrayhash-map
easy
Palindrome Checker
easy
Two Sum II - Input Array Is Sorted
two-pointers
medium
3Sum
two-pointers
medium
Container With Most Water
two-pointers
medium
Trapping Rain Water
two-pointers
hard
Maximal Rectangle
stack
hard