Minimum Number of Platforms

Problem

Given train arrival and departure times, find the minimum number of platforms needed so no train waits.

Example

arr=[900,940,950,1100], dep=[910,1200,1120,1130] -> 3

Constraints

• 1 ≤ n ≤ 10^5

Approach

Sort arrivals and departures; sweep with two pointers tracking concurrent trains. Reported ServiceNow question.