Maintain the First Value That Appears Exactly Once
Company: Uber
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: hard
Interview Round: Technical Screen
Quick Answer: Practice a Uber coding interview problem focused on maintain the first value that appears exactly once. The prompt emphasizes edge cases, clean implementation, and verifiable test behavior without revealing the solution.
Examples
Input: {"initial":[2,3,5],"operations":[["show"],["add",5],["show"],["add",2],["show"],["add",3],["show"]]}
Expected Output: [2,2,3,-1]
Explanation: Classic stream.
Input: {"initial":[],"operations":[["show"]]}
Expected Output: [-1]
Explanation: Empty.
Input: {"initial":[1,1],"operations":[["show"]]}
Expected Output: [-1]
Explanation: No unique.
Input: {"initial":[1,2,1],"operations":[["show"]]}
Expected Output: [2]
Explanation: First remaining unique.
Input: {"initial":[7],"operations":[["show"],["add",7],["show"]]}
Expected Output: [7,-1]
Explanation: Unique becomes duplicate.
Input: {"initial":[1,2],"operations":[["add",3],["show"]]}
Expected Output: [1]
Explanation: Oldest unique.
Input: {"initial":[1,1,2],"operations":[["add",2],["add",3],["show"]]}
Expected Output: [3]
Explanation: New unique.
Input: {"initial":[4,5,4,6],"operations":[["show"],["add",5],["show"]]}
Expected Output: [5,6]
Explanation: Queue cleanup.