Citadel vs X Interview Questions
Citadel lists 101 LeetCode interview questions while X lists 51. They share 11 problems — 11% of Citadel's bank and 22% of X's. Focus on the overlap first, then drill into 90 Citadel-only and 40 X-only questions.
Overview
Preparation Strategy
Step 1 — Shared core: Solve the 11 overlapping problems first. These are the highest-yield questions for candidates interviewing at both Citadel and X.
Step 2 — Company-specific depth: Add Citadel-specific problems like Longest Non-decreasing Subarray From Two Arrays, Binary Tree Maximum Path Sum, Minimum Knight Moves and X-specific problems from the exclusive lists below.
Step 3 — Difficulty tuning: Citadel skews harder in our data. Budget extra time for Hard problems if you are targeting that company.
Difficulty Comparison
Top Shared Topics
11 Shared Questions
High-priority problems to practice for both Citadel and X.
| Problem | Difficulty |
|---|---|
| LRU Cache | Medium |
| Merge Intervals | Medium |
| Insert Delete GetRandom O(1) | Medium |
| Merge k Sorted Lists | Hard |
| Trapping Rain Water | Hard |
| Regular Expression Matching | Hard |
| Implement Trie (Prefix Tree) | Medium |
| Alien Dictionary | Hard |
| Max Points on a Line | Hard |
| The Skyline Problem | Hard |
| Integer to Roman | Medium |
Unique to Citadel (90)
Problems in Citadel's list that do not appear at X.
Unique to X (40)
Problems in X's list that do not appear at Citadel.
| Problem | Difficulty |
|---|---|
| Tweet Counts Per Frequency | Medium |
| Flatten Nested List Iterator | Medium |
| Design Twitter | Medium |
| Binary Gap | Easy |
| Word Break II | Hard |
| Time Needed to Buy Tickets | Easy |
| Valid Parentheses | Easy |
| Trapping Rain Water II | Hard |
| Finding the Users Active Minutes | Medium |
| One Edit Distance | Medium |
| Invalid Tweets | Easy |
| Best Meeting Point | Hard |
Frequently Asked Questions
How many LeetCode questions do Citadel and X share?
Citadel and X share 11 LeetCode interview questions. 90 problems appear only in Citadel's list and 40 appear only in X's list.
What topics overlap most between Citadel and X?
The most common shared topics between Citadel and X are Array (6 shared questions), Hash Table (5 shared questions), String (4 shared questions), Design (3 shared questions), Math (3 shared questions). Mastering these areas prepares you for both companies.
Which company asks harder LeetCode questions: Citadel or X?
Citadel has 5 Easy, 60 Medium, and 36 Hard questions. X has 8 Easy, 31 Medium, and 12 Hard questions. Citadel has a higher proportion of Hard problems in its interview set.
How should I prepare if interviewing at both Citadel and X?
Start with the 11 shared problems since they cover what both companies ask most often. Then add 20 Citadel-specific and 20 X-specific questions to round out your prep.