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Citadel LeetCode Questions 2026

Browse LeetCode problems frequently asked by Citadel. Filter by difficulty and timeframe to focus your interview prep.

Last updated: 20 Feb 2026

Timeframe

Difficulty

Problem	Difficulty	Frequency	Topics
Regular Expression Matching	HARD	50%	StringDynamic ProgrammingRecursion
Merge k Sorted Lists	HARD	50%	Linked ListDivide and ConquerHeap (Priority Queue)Merge Sort
Sudoku Solver	HARD	50%	ArrayHash TableBacktrackingMatrix
Combination Sum	MEDIUM	50%	ArrayBacktracking
Trapping Rain Water	HARD	50%	ArrayTwo PointersDynamic ProgrammingStackMonotonic Stack
Permutations	MEDIUM	50%	ArrayBacktracking
Simplify Path	MEDIUM	50%	StringStack
Minimum Equal Sum of Two Arrays After Replacing Zeros	MEDIUM	75%	ArrayGreedy
Longest String Chain	MEDIUM	75%	ArrayHash TableTwo PointersStringDynamic ProgrammingSorting
Minimum Knight Moves	MEDIUM	62.5%	Breadth-First Search
Best Time to Buy and Sell Stock	EASY	87.5%	ArrayDynamic Programming
Best Time to Buy and Sell Stock III	HARD	50%	ArrayDynamic Programming
Binary Tree Maximum Path Sum	HARD	50%	Dynamic ProgrammingTreeDepth-First SearchBinary Tree
LRU Cache	MEDIUM	75%	Hash TableLinked ListDesignDoubly-Linked List
Evaluate Reverse Polish Notation	MEDIUM	75%	ArrayMathStack
Number of Islands	MEDIUM	62.5%	ArrayDepth-First SearchBreadth-First SearchUnion-FindMatrix
Course Schedule	MEDIUM	50%	Depth-First SearchBreadth-First SearchGraph TheoryTopological Sort
Maximal Square	MEDIUM	50%	ArrayDynamic ProgrammingMatrix
Sliding Window Maximum	HARD	100%	ArrayQueueSliding WindowHeap (Priority Queue)Monotonic Queue
Perfect Squares	MEDIUM	50%	MathDynamic ProgrammingBreadth-First Search

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