Airport Gate Allocation

You are given two arrays of equal length:

• arrival: An array of integers where each element represents the arrival time of a flight.
• departure: An array of integers where each element represents the departure time of the corresponding flight.

Each flight occupies a gate from its arrival time up to, but not including, its departure time. Your task is to write a function that calculates the minimum number of gates required so that all flights can be scheduled without any overlapping gate usage.

Example

Suppose the input arrays are:

arrival   = [900, 940, 950, 1100, 1500, 1800]
departure = [910, 1200, 1120, 1130, 1900, 2000]

Your function should return the minimum number of gates needed to handle the flights without conflicts.

Constraints:

• The lengths of the arrival and departure arrays are equal.
• The times are represented as integers (e.g., minutes or 24-hour clock values).
• You may assume that the departure time of a flight is always after its arrival time.

Develop a solution that efficiently computes the minimum number of gates required.