Russian Doll Envelopes
You have a list of envelopes, who each have an integer width and height. An envelope can fit into another envelope if and only if the first envelope's width and height is smaller than the other envelope's width and height (you cannot rotate either envelopes).
Given a list of envelopes, find the maximum number of envelopes that you can fit inside one another like a Russian Doll.
Input & Output
Input
envelopes — a list of integer pairings representing the envelopes. For each pair, the first integer represents the width, and the second integer represents the height.
Output
The number representing the max envelope layers.
Example
Input
envelopes = [[5, 4], [6, 4], [6, 7], [2, 3]]
Output
3
Explanation
[2, 3] goes inside [5, 4], which goes inside [6, 7]
Constraints
1 <= len(envelopes) <= 50001 <= width[i], height[i] <= 10^4