Section 1Understand Problem
Section 01
Understand the problem
Restate the problem precisely. Interviewers reward candidates who pause, define the contract, and name the guarantees before coding.
Problem statement
You are given an array of `n` pairs `pairs` where `pairs[i] = [lefti, righti]` and `lefti < righti`. A pair `p2 = [c, d]` follows a pair `p1 = [a, b]` if `b < c`. A chain of pairs can be formed in this fashion. Return the length of the longest chain which can be formed. You do not need to use up all the given intervals. You can select pairs in any order.
Example
pairs = [[1,2],[2,3],[3,4]] → 2
Constraints
n == pairs.length · 1 ≤ n ≤ 1000 · −1000 ≤ lefti < righti ≤ 1000
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