Last Substring in Lexicographical Order

HardStringstwo pointers

Solve this the way you would in the interview: out loud, on a timer, with an AI interviewer asking follow-ups while you code. You get a scored report at the end.

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Problem

Given a string s, consider all of its non-empty substrings and return the one that comes **last** in lexicographical order. The answer is always a suffix of s, because extending a substring to the right only makes it larger. So the task is to find the lexicographically largest suffix. Aim for O(n) time and O(1) extra space beyond the output.

Examples

Input: s = "abab"
Output: "bab"
The suffixes are "abab", "bab", "ab" and "b". The largest is "bab".
Input: s = "zanzibar"
Output: "zibar"
Both suffixes starting with z are candidates, and "zibar" beats "zanzibar" at the second character.

Constraints

  • 1 <= s.length <= 4 * 10^5
  • `s` consists of lowercase English letters

What the interviewer grades

A correct solution is one of five scores. The report also grades problem understanding (did you clarify inputs and edge cases before coding), problem solving, communication while you work, code quality, and testing. See a sample report, or read up on the pattern in the lessons.

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