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Find Missing Number is a easy coding interview question covering arrays, math — the kind asked at FAANG (Facebook/Meta, Apple, Amazon, Netflix, Google) and AI-first companies like Anthropic, OpenAI, and Nvidia.
Given an array nums containing n distinct numbers in the range [0, n], return the one number that is missing.
Example: [3,0,1] -> 2 Example: [9,6,4,2,3,5,7,0,1] -> 8
Implement in O(1) extra space and O(n) time. Bonus: implement using XOR instead of the sum formula.
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