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Solve palindrome and missing-number variants

AristaSoftware Engineer · Technical Screen
EasySoftware EngineerTechnical ScreenCoding & Algorithms

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This question evaluates competencies in string processing, array manipulation, binary search, and algorithmic complexity analysis by asking a palindrome check and a missing-number problem that requires both O(n) and O(log n) reasoning, emphasizing edge-case handling and time/space complexity discussion.

You are asked to solve two coding problems and analyze the time and space complexity of each.

  1. Palindrome check Given a string s, determine whether it reads the same forward and backward. Treat the empty string as a valid palindrome. If s is null, return false.

  2. Missing number with arbitrary start Given a sorted array nums of distinct integers, the values should form a consecutive sequence with step size 1, but exactly one number is missing. The sequence does not necessarily start at 0.

Examples:

  • [4, 5, 6, 8, 9] -> 7
  • [10, 11, 13] -> 12

First describe an O(n) solution, then improve it to an O(log n) solution using binary search.

For both problems, be prepared to explain your time and space complexity and discuss edge cases.