Daily Coding Problem — Solutions

C++ solutions to the Daily Coding Problem newsletter. README is auto-generated.

📊 Stats

🟢 Easy	🟡 Medium	🔴 Hard	Total
22	30	20	72

🏷️ By Topic

Arrays  ·  17 problem(s)

Problem	Difficulty	File
Two Sum Check	🟢 Easy	26_09_2025.cpp
Maximum Profit from Stock Prices	🟢 Easy	12_11_2025.cpp
Maximum Product of Three Numbers	🟢 Easy	04_12_2025.cpp
Product Array Excluding Self	🔴 Hard	27_09_2025.cpp
First Missing Positive Integer	🔴 Hard	29_09_2025.cpp
Largest Sum of Non-Adjacent Numbers	🔴 Hard	04_10_2025.cpp
Find Unique Among Triplicates	🔴 Hard	05_11_2025.cpp
Subset Sum to Target	🔴 Hard	07_11_2025.cpp
Minimum Cost to Paint Houses	🟡 Medium	14_10_2025.cpp
Reconstruct Sentence from Dictionary	🟡 Medium	17_10_2025.cpp
Trapping Rainwater	🟡 Medium	25_10_2025.cpp
Count Array Inversions	🟡 Medium	09_11_2025.cpp
Maximum Sum Contiguous Subarray	🟡 Medium	14_11_2025.cpp
Shuffle Deck with Uniform Probability	🟡 Medium	16_11_2025.cpp
Search in Rotated Sorted Array	🟡 Medium	23_11_2025.cpp
Partition Multiset Into Equal Sums	🟡 Medium	25_11_2025.cpp
Count Attacking Bishop Pairs	🟡 Medium	03_12_2025.cpp

Strings  ·  16 problem(s)

Problem	Difficulty	File
Find First Recurring Character	🟢 Easy	12_04_2026.cpp
Balanced Brackets Validator	🟢 Easy	22_10_2025.cpp
Run-Length Encoding and Decoding	🟢 Easy	24_10_2025.cpp
Edit Distance Between Two Strings	🟢 Easy	26_10_2025.cpp
URL Shortener with Restore	🟢 Easy	20_11_2025.cpp
Word Search in 2D Matrix	🟢 Easy	28_11_2025.cpp
Longest Substring with K Distinct Characters	🔴 Hard	08_10_2025.cpp
Longest Absolute File Path	🔴 Hard	12_10_2025.cpp
Regular Expression Matching	🔴 Hard	20_10_2025.cpp
Longest Palindromic Substring	🔴 Hard	11_11_2025.cpp
Count Ways to Decode Message	🟡 Medium	02_10_2025.cpp
Autocomplete System with Trie	🟡 Medium	06_10_2025.cpp
Reconstruct Sentence from Dictionary	🟡 Medium	17_10_2025.cpp
Full Text Justification	🟡 Medium	23_10_2025.cpp
Minimum Insertions to Make Palindrome	🟡 Medium	29_10_2025.cpp
Break String Into Lines of Max Width	🟡 Medium	22_11_2025.cpp

Hash Table  ·  7 problem(s)

Problem	Difficulty	File
Find First Recurring Character	🟢 Easy	12_04_2026.cpp
Two Sum Check	🟢 Easy	26_09_2025.cpp
URL Shortener with Restore	🟢 Easy	20_11_2025.cpp
Longest Substring with K Distinct Characters	🔴 Hard	08_10_2025.cpp
LRU Cache Implementation	🔴 Hard	17_11_2025.cpp
LFU Cache Implementation	🔴 Hard	02_12_2025.cpp
Count Attacking Bishop Pairs	🟡 Medium	03_12_2025.cpp

Two Pointers  ·  5 problem(s)

Problem	Difficulty	File
Find Intersecting Linked List Node	🟢 Easy	15_10_2025.cpp
Maximum Profit from Stock Prices	🟢 Easy	12_11_2025.cpp
Sort RGB Array In-Place	🔴 Hard	30_10_2025.cpp
Remove Kth Last Linked List Node	🟡 Medium	21_10_2025.cpp
Trapping Rainwater	🟡 Medium	25_10_2025.cpp

Sliding Window  ·  2 problem(s)

Problem	Difficulty	File
Longest Substring with K Distinct Characters	🔴 Hard	08_10_2025.cpp
Maximum Value in Each Sliding Window	🔴 Hard	13_10_2025.cpp

Linked Lists  ·  5 problem(s)

Problem	Difficulty	File
Find Intersecting Linked List Node	🟢 Easy	15_10_2025.cpp
XOR Memory-Efficient Doubly Linked List	🔴 Hard	01_10_2025.cpp
LRU Cache Implementation	🔴 Hard	17_11_2025.cpp
LFU Cache Implementation	🔴 Hard	02_12_2025.cpp
Remove Kth Last Linked List Node	🟡 Medium	21_10_2025.cpp

Stack  ·  4 problem(s)

Problem	Difficulty	File
Balanced Brackets Validator	🟢 Easy	22_10_2025.cpp
Max Stack with O(1) Maximum	🟢 Easy	08_11_2025.cpp
Longest Absolute File Path	🔴 Hard	12_10_2025.cpp
Queue Implemented Using Two Stacks	🟡 Medium	18_11_2025.cpp

Queue  ·  3 problem(s)

Problem	Difficulty	File
Fixed-Size Order Log	🟢 Easy	11_10_2025.cpp
Maximum Value in Each Sliding Window	🔴 Hard	13_10_2025.cpp
Queue Implemented Using Two Stacks	🟡 Medium	18_11_2025.cpp

Trees  ·  7 problem(s)

Problem	Difficulty	File
Count Unival Subtrees	🟢 Easy	03_10_2025.cpp
Evaluate Arithmetic Expression Tree	🟢 Easy	15_11_2025.cpp
Serialize and Deserialize Binary Tree	🟡 Medium	28_09_2025.cpp
Autocomplete System with Trie	🟡 Medium	06_10_2025.cpp
Locking Binary Tree Nodes	🟡 Medium	19_10_2025.cpp
Second Largest Node in BST	🟡 Medium	31_10_2025.cpp
Reconstruct Tree from Traversals	🟡 Medium	13_11_2025.cpp

Graphs  ·  4 problem(s)

Problem	Difficulty	File
Shortest Path in Boolean Grid	🟢 Easy	18_10_2025.cpp
Detect Currency Arbitrage	🔴 Hard	27_10_2025.cpp
Reconstruct Flight Itinerary	🟡 Medium	06_11_2025.cpp
Graph K-Coloring	🟡 Medium	21_11_2025.cpp

Heap  ·  2 problem(s)

Problem	Difficulty	File
Minimum Rooms for Overlapping Lectures	🟢 Easy	16_10_2025.cpp
Running Median of Number Stream	🟢 Easy	28_10_2025.cpp

Binary Search  ·  2 problem(s)

Problem	Difficulty	File
Second Largest Node in BST	🟡 Medium	31_10_2025.cpp
Search in Rotated Sorted Array	🟡 Medium	23_11_2025.cpp

Sorting  ·  4 problem(s)

Problem	Difficulty	File
Minimum Rooms for Overlapping Lectures	🟢 Easy	16_10_2025.cpp
Maximum Product of Three Numbers	🟢 Easy	04_12_2025.cpp
Sort RGB Array In-Place	🔴 Hard	30_10_2025.cpp
Count Array Inversions	🟡 Medium	09_11_2025.cpp

Dynamic Programming  ·  12 problem(s)

Problem	Difficulty	File
Edit Distance Between Two Strings	🟢 Easy	26_10_2025.cpp
Largest Sum of Non-Adjacent Numbers	🔴 Hard	04_10_2025.cpp
Count Ways to Climb Staircase	🔴 Hard	07_10_2025.cpp
Regular Expression Matching	🔴 Hard	20_10_2025.cpp
Subset Sum to Target	🔴 Hard	07_11_2025.cpp
Longest Palindromic Substring	🔴 Hard	11_11_2025.cpp
Count Ways to Decode Message	🟡 Medium	02_10_2025.cpp
Minimum Cost to Paint Houses	🟡 Medium	14_10_2025.cpp
Minimum Insertions to Make Palindrome	🟡 Medium	29_10_2025.cpp
Maximum Sum Contiguous Subarray	🟡 Medium	14_11_2025.cpp
Partition Multiset Into Equal Sums	🟡 Medium	25_11_2025.cpp
Count Paths in Grid Moving Right/Down	🟡 Medium	27_11_2025.cpp

Recursion  ·  8 problem(s)

Problem	Difficulty	File
Count Unival Subtrees	🟢 Easy	03_10_2025.cpp
Generate Power Set	🟢 Easy	01_11_2025.cpp
Evaluate Arithmetic Expression Tree	🟢 Easy	15_11_2025.cpp
Count Ways to Climb Staircase	🔴 Hard	07_10_2025.cpp
Count N-Queens Arrangements	🔴 Hard	02_11_2025.cpp
Count Knight's Tours on Chessboard	🔴 Hard	29_11_2025.cpp
Reconstruct Tree from Traversals	🟡 Medium	13_11_2025.cpp
Fast Integer Exponentiation	🟡 Medium	26_11_2025.cpp

Backtracking  ·  4 problem(s)

Problem	Difficulty	File
Count N-Queens Arrangements	🔴 Hard	02_11_2025.cpp
Sudoku Solver	🔴 Hard	19_11_2025.cpp
Count Knight's Tours on Chessboard	🔴 Hard	29_11_2025.cpp
Graph K-Coloring	🟡 Medium	21_11_2025.cpp

Greedy  ·  3 problem(s)

Problem	Difficulty	File
Full Text Justification	🟡 Medium	23_10_2025.cpp
Reconstruct Flight Itinerary	🟡 Medium	06_11_2025.cpp
Break String Into Lines of Max Width	🟡 Medium	22_11_2025.cpp

Math  ·  7 problem(s)

Problem	Difficulty	File
Implement Rand7 from Rand5	🟢 Easy	10_11_2025.cpp
Nth Number with Digit Sum Ten	🟢 Easy	05_12_2025.cpp
Implement Rand5 from Rand7	🟢 Easy	06_12_2025.cpp
Monte Carlo Estimation of Pi	🟡 Medium	09_10_2025.cpp
Shuffle Deck with Uniform Probability	🟡 Medium	16_11_2025.cpp
Fast Integer Exponentiation	🟡 Medium	26_11_2025.cpp
Simulate Unbiased Coin from Biased	🟡 Medium	01_12_2025.cpp

Bit Manipulation  ·  3 problem(s)

Problem	Difficulty	File
Generate Power Set	🟢 Easy	01_11_2025.cpp
XOR Memory-Efficient Doubly Linked List	🔴 Hard	01_10_2025.cpp
Find Unique Among Triplicates	🔴 Hard	05_11_2025.cpp

Matrix  ·  6 problem(s)

Problem	Difficulty	File
Shortest Path in Boolean Grid	🟢 Easy	18_10_2025.cpp
Word Search in 2D Matrix	🟢 Easy	28_11_2025.cpp
Print Matrix in Clockwise Spiral	🟢 Easy	30_11_2025.cpp
Sudoku Solver	🔴 Hard	19_11_2025.cpp
Conway's Game of Life	🟡 Medium	04_11_2025.cpp
Count Paths in Grid Moving Right/Down	🟡 Medium	27_11_2025.cpp

Other  ·  6 problem(s)

Problem	Difficulty	File
File Syncing Algorithm Design	🔴 Hard	24_11_2025.cpp
Functional Cons Car Cdr with Closures	🟡 Medium	30_09_2025.cpp
Delayed Job Scheduler	🟡 Medium	05_10_2025.cpp
Random Element from Data Stream	🟡 Medium	10_10_2025.cpp
Conway's Game of Life	🟡 Medium	04_11_2025.cpp
Simulate Unbiased Coin from Biased	🟡 Medium	01_12_2025.cpp

📋 All Problems

Problem	Topics	Difficulty	File
Find First Recurring Character	strings hash-table	🟢 Easy	12_04_2026.cpp
Two Sum Check	arrays hash-table	🟢 Easy	26_09_2025.cpp
Count Unival Subtrees	trees recursion	🟢 Easy	03_10_2025.cpp
Fixed-Size Order Log	queue	🟢 Easy	11_10_2025.cpp
Find Intersecting Linked List Node	linked-lists two-pointers	🟢 Easy	15_10_2025.cpp
Minimum Rooms for Overlapping Lectures	heap sorting	🟢 Easy	16_10_2025.cpp
Shortest Path in Boolean Grid	graphs matrix	🟢 Easy	18_10_2025.cpp
Balanced Brackets Validator	strings stack	🟢 Easy	22_10_2025.cpp
Run-Length Encoding and Decoding	strings	🟢 Easy	24_10_2025.cpp
Edit Distance Between Two Strings	dynamic-programming strings	🟢 Easy	26_10_2025.cpp
Running Median of Number Stream	heap	🟢 Easy	28_10_2025.cpp
Generate Power Set	bit-manipulation recursion	🟢 Easy	01_11_2025.cpp
Max Stack with O(1) Maximum	stack	🟢 Easy	08_11_2025.cpp
Implement Rand7 from Rand5	math	🟢 Easy	10_11_2025.cpp
Maximum Profit from Stock Prices	arrays two-pointers	🟢 Easy	12_11_2025.cpp
Evaluate Arithmetic Expression Tree	trees recursion	🟢 Easy	15_11_2025.cpp
URL Shortener with Restore	hash-table strings	🟢 Easy	20_11_2025.cpp
Word Search in 2D Matrix	matrix strings	🟢 Easy	28_11_2025.cpp
Print Matrix in Clockwise Spiral	matrix	🟢 Easy	30_11_2025.cpp
Maximum Product of Three Numbers	arrays sorting	🟢 Easy	04_12_2025.cpp
Nth Number with Digit Sum Ten	math	🟢 Easy	05_12_2025.cpp
Implement Rand5 from Rand7	math	🟢 Easy	06_12_2025.cpp
Product Array Excluding Self	arrays	🔴 Hard	27_09_2025.cpp
First Missing Positive Integer	arrays	🔴 Hard	29_09_2025.cpp
XOR Memory-Efficient Doubly Linked List	linked-lists bit-manipulation	🔴 Hard	01_10_2025.cpp
Largest Sum of Non-Adjacent Numbers	dynamic-programming arrays	🔴 Hard	04_10_2025.cpp
Count Ways to Climb Staircase	dynamic-programming recursion	🔴 Hard	07_10_2025.cpp
Longest Substring with K Distinct Characters	sliding-window strings hash-table	🔴 Hard	08_10_2025.cpp
Longest Absolute File Path	stack strings	🔴 Hard	12_10_2025.cpp
Maximum Value in Each Sliding Window	sliding-window queue	🔴 Hard	13_10_2025.cpp
Regular Expression Matching	dynamic-programming strings	🔴 Hard	20_10_2025.cpp
Detect Currency Arbitrage	graphs	🔴 Hard	27_10_2025.cpp
Sort RGB Array In-Place	sorting two-pointers	🔴 Hard	30_10_2025.cpp
Count N-Queens Arrangements	backtracking recursion	🔴 Hard	02_11_2025.cpp
Find Unique Among Triplicates	bit-manipulation arrays	🔴 Hard	05_11_2025.cpp
Subset Sum to Target	dynamic-programming arrays	🔴 Hard	07_11_2025.cpp
Longest Palindromic Substring	dynamic-programming strings	🔴 Hard	11_11_2025.cpp
LRU Cache Implementation	hash-table linked-lists	🔴 Hard	17_11_2025.cpp
Sudoku Solver	backtracking matrix	🔴 Hard	19_11_2025.cpp
File Syncing Algorithm Design	other	🔴 Hard	24_11_2025.cpp
Count Knight's Tours on Chessboard	backtracking recursion	🔴 Hard	29_11_2025.cpp
LFU Cache Implementation	hash-table linked-lists	🔴 Hard	02_12_2025.cpp
Serialize and Deserialize Binary Tree	trees	🟡 Medium	28_09_2025.cpp
Functional Cons Car Cdr with Closures	other	🟡 Medium	30_09_2025.cpp
Count Ways to Decode Message	dynamic-programming strings	🟡 Medium	02_10_2025.cpp
Delayed Job Scheduler	other	🟡 Medium	05_10_2025.cpp
Autocomplete System with Trie	trees strings	🟡 Medium	06_10_2025.cpp
Monte Carlo Estimation of Pi	math	🟡 Medium	09_10_2025.cpp
Random Element from Data Stream	other	🟡 Medium	10_10_2025.cpp
Minimum Cost to Paint Houses	dynamic-programming arrays	🟡 Medium	14_10_2025.cpp
Reconstruct Sentence from Dictionary	strings arrays	🟡 Medium	17_10_2025.cpp
Locking Binary Tree Nodes	trees	🟡 Medium	19_10_2025.cpp
Remove Kth Last Linked List Node	linked-lists two-pointers	🟡 Medium	21_10_2025.cpp
Full Text Justification	strings greedy	🟡 Medium	23_10_2025.cpp
Trapping Rainwater	two-pointers arrays	🟡 Medium	25_10_2025.cpp
Minimum Insertions to Make Palindrome	dynamic-programming strings	🟡 Medium	29_10_2025.cpp
Second Largest Node in BST	trees binary-search	🟡 Medium	31_10_2025.cpp
Conway's Game of Life	matrix other	🟡 Medium	04_11_2025.cpp
Reconstruct Flight Itinerary	graphs greedy	🟡 Medium	06_11_2025.cpp
Count Array Inversions	sorting arrays	🟡 Medium	09_11_2025.cpp
Reconstruct Tree from Traversals	trees recursion	🟡 Medium	13_11_2025.cpp
Maximum Sum Contiguous Subarray	dynamic-programming arrays	🟡 Medium	14_11_2025.cpp
Shuffle Deck with Uniform Probability	arrays math	🟡 Medium	16_11_2025.cpp
Queue Implemented Using Two Stacks	stack queue	🟡 Medium	18_11_2025.cpp
Graph K-Coloring	graphs backtracking	🟡 Medium	21_11_2025.cpp
Break String Into Lines of Max Width	strings greedy	🟡 Medium	22_11_2025.cpp
Search in Rotated Sorted Array	binary-search arrays	🟡 Medium	23_11_2025.cpp
Partition Multiset Into Equal Sums	dynamic-programming arrays	🟡 Medium	25_11_2025.cpp
Fast Integer Exponentiation	math recursion	🟡 Medium	26_11_2025.cpp
Count Paths in Grid Moving Right/Down	dynamic-programming matrix	🟡 Medium	27_11_2025.cpp
Simulate Unbiased Coin from Biased	math other	🟡 Medium	01_12_2025.cpp
Count Attacking Bishop Pairs	arrays hash-table	🟡 Medium	03_12_2025.cpp