Citadel Interview Questions — 100 DSA Problems

88 problems with full solutions in Python, Java, C++, JavaScript, Go, Rust.

Most frequently asked Citadel LeetCode questions for software engineering interviews.

• Longest Non-decreasing Subarray From Two Arrays (MEDIUM) — Array, Dynamic Programming
• Binary Tree Maximum Path Sum (HARD) — Dynamic Programming, Tree, Depth-First Search, Binary Tree
• Delete and Earn (MEDIUM) — Array, Hash Table, Dynamic Programming
• Minimum Knight Moves (MEDIUM) — Breadth-First Search
• Palindromic Substrings (MEDIUM) — Two Pointers, String, Dynamic Programming
• Sliding Window Maximum (HARD) — Array, Queue, Sliding Window, Heap (Priority Queue), Monotonic Queue
• Count Palindromic Subsequences (HARD) — String, Dynamic Programming
• Minimum Equal Sum of Two Arrays After Replacing Zeros (MEDIUM) — Array, Greedy
• LFU Cache (HARD) — Hash Table, Linked List, Design, Doubly-Linked List
• Minimum Operations to Make Numbers Non-positive (HARD) — Array, Binary Search
• Number of Good Binary Strings (MEDIUM) — Dynamic Programming
• Maximum Total Damage With Spell Casting (MEDIUM) — Array, Hash Table, Two Pointers, Binary Search, Dynamic Programming, Sorting, Counting
• Maximum Length of Repeated Subarray (MEDIUM) — Array, Binary Search, Dynamic Programming, Sliding Window, Rolling Hash, Hash Function
• LRU Cache (MEDIUM) — Hash Table, Linked List, Design, Doubly-Linked List
• Minimum Costs Using the Train Line (HARD) — Array, Dynamic Programming
• Best Position for a Service Centre (HARD) — Array, Math, Geometry, Randomized
• Evaluate Division (MEDIUM) — Array, String, Depth-First Search, Breadth-First Search, Union Find, Graph, Shortest Path
• First Completely Painted Row or Column (MEDIUM) — Array, Hash Table, Matrix
• Longest String Chain (MEDIUM) — Array, Hash Table, Two Pointers, String, Dynamic Programming, Sorting
• Merge Intervals (MEDIUM) — Array, Sorting
• Best Time to Buy and Sell Stock (EASY) — Array, Dynamic Programming
• Serialize and Deserialize Binary Tree (HARD) — String, Tree, Depth-First Search, Breadth-First Search, Design, Binary Tree
• Find the Duplicate Number (MEDIUM) — Array, Two Pointers, Binary Search, Bit Manipulation
• Evaluate Reverse Polish Notation (MEDIUM) — Array, Math, Stack
• Insert Delete GetRandom O(1) (MEDIUM) — Array, Hash Table, Math, Design, Randomized
• Sudoku Solver (HARD) — Array, Hash Table, Backtracking, Matrix
• Length of Longest Subarray With at Most K Frequency (MEDIUM) — Array, Hash Table, Sliding Window
• Parallel Courses III (HARD) — Array, Dynamic Programming, Graph, Topological Sort
• Number of Islands (MEDIUM) — Array, Depth-First Search, Breadth-First Search, Union Find, Matrix
• Couples Holding Hands (HARD) — Greedy, Depth-First Search, Breadth-First Search, Union Find, Graph
• Find Median from Data Stream (HARD) — Two Pointers, Design, Sorting, Heap (Priority Queue), Data Stream
• Group Anagrams (MEDIUM) — Array, Hash Table, String, Sorting
• Validate Binary Search Tree (MEDIUM) — Tree, Depth-First Search, Binary Search Tree, Binary Tree
• Meeting Scheduler (MEDIUM) — Array, Two Pointers, Sorting
• Employee Free Time (HARD) — Array, Line Sweep, Sorting, Heap (Priority Queue)
• Merge k Sorted Lists (HARD) — Linked List, Divide and Conquer, Heap (Priority Queue), Merge Sort
• Permutations (MEDIUM) — Array, Backtracking
• Robot Room Cleaner (HARD) — Backtracking, Interactive
• Binary Tree Zigzag Level Order Traversal (MEDIUM) — Tree, Breadth-First Search, Binary Tree
• Design Search Autocomplete System (HARD) — String, Depth-First Search, Design, Trie, Sorting, Heap (Priority Queue), Data Stream
• N-Queens (HARD) — Array, Backtracking
• Fizz Buzz (EASY) — Math, String, Simulation
• Best Time to Buy and Sell Stock II (MEDIUM) — Array, Dynamic Programming, Greedy
• Regular Expression Matching (HARD) — String, Dynamic Programming, Recursion
• Best Time to Buy and Sell Stock III (HARD) — Array, Dynamic Programming
• Search Suggestions System (MEDIUM) — Array, String, Binary Search, Trie, Sorting, Heap (Priority Queue)
• Combination Sum (MEDIUM) — Array, Backtracking
• Design Circular Queue (MEDIUM) — Array, Linked List, Design, Queue
• Trapping Rain Water (HARD) — Array, Two Pointers, Dynamic Programming, Stack, Monotonic Stack
• Word Search (MEDIUM) — Array, String, Backtracking, Depth-First Search, Matrix