题目：
题解：
class Solution:def maxEnvelopes(self, envelopes: List[List[int]]) -> int:if not envelopes:return 0n = len(envelopes)envelopes.sort(key=lambda x: (x[0], -x[1]))f = [1] * nfor i in range(n):for j in range(i):if envelopes[j][1] < envelopes[i][1]:f[i] = max(f[i], f[j] + 1)return max(f)
