How to realize Russian doll envelope by leetcode

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Given some envelopes marked with width and height, width and height appear in integer pairs (w, h). When the width and height of another envelope are larger than this envelope, this envelope can be put into another envelope, just like the Russian doll.

Please calculate the maximum number of envelopes that can form a group of "Russian doll" envelopes (that is, you can put one envelope into another).

Description:

Rotating envelopes is not allowed.

Example:

Input: envelopes = [[5jue 4], [6je 4], [6pr 7], [2pr 3]]

Output: 3

Explanation: the maximum number of envelopes is 3, and the combination is: [2jue 3] = > [5je 4] = > [6je 7].

Ideas for solving the problem:

1, this is a two-dimensional sorting + lis compound problem

2, first do the two-dimensional sorting, install the first dimensional ascending order, and the second dimension describe the arrangement

3, do lis for the second dimension

A, denote the longest increasing subsequence at the end of I by dp [I]

B, then if a [I] > a [j], dp [I] = a [j] + 1

C, for j from 0 to I, take the maximum value

4. Note that the maximum value needs to traverse the dp

Code implementation

Func maxEnvelopes (envelopes [] int) int {if len (envelopes)