Increasing Triplet Subsequence

MediumGreedygreedy

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 an integer array nums, determine whether there exist indices i < j < k such that nums[i] < nums[j] < nums[k] (strictly increasing). Return true if such a triple exists and false otherwise. Aim for O(n) time and O(1) extra space.

Examples

Input: nums = [5,1,4,2,3]
Output: true
Indices 1, 3, 4 give 1 < 2 < 3.
Input: nums = [4,4,3,2]
Output: false
The array never strictly increases.

Constraints

  • 1 <= nums.length <= 5 * 10^5
  • -2^31 <= nums[i] <= 2^31 - 1

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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