Russian Doll Envelopes

HardDynamic ProgrammingDynamic Programming

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

You are given a 2D array of integers envelopes where envelopes[i] = [w_i, h_i] represents the width and the height of an envelope. One envelope can fit into another if and only if both the width and height of one envelope are greater than the other envelope's width and height. Return the maximum number of envelopes you can Russian doll (i.e., put one inside the other). Note: You cannot rotate an envelope.

Examples

Input: envelopes = [[5,4],[6,4],[6,7],[2,3]]
Output: 3
The maximum number of envelopes you can Russian doll is 3 ([2,3] => [5,4] => [6,7]).
Input: envelopes = [[1,1],[1,1],[1,1]]
Output: 1

Constraints

  • 1 <= envelopes.length <= 10^5
  • envelopes[i].length == 2
  • 1 <= w_i, h_i <= 10^5

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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