# What is the solution to a Busy Intersection LeetCode?

A busy intersection leetcode is a common phenomenon in many cities, where a large number of vehicles and pedestrians cross paths at the same time. This creates a challenging situation for traffic management and requires efficient algorithms to ensure safety and smooth flow.

In this article, we will explore the problem of modeling a busy intersection in the context of LeetCode, a popular platform for preparing coding interviews and practicing algorithmic skills.

## Problem Statement

Given a list of cars, each car has a unique identifier, an arrival time, and a direction. Cars are either traveling North/South or East/West and they arrive at the intersection at different times. Our task is to determine the number of cars that will cross the intersection.

The rules for the cars crossing the intersection are as follows:

A car can only cross the intersection if there are no other cars in its path.

A car traveling North/South cannot cross the intersection if there is a car traveling East/West and vice versa.

Cars that arrive at the same time can cross the intersection in any order.

The problem can be further divided into two sub-problems:

Modeling the state of the intersection at any given time.

Determining the number of cars that cross the intersection.

## Approach

To solve the busy intersection problem, we will use a queue-based approach, where we maintain two separate queues for cars traveling in opposite directions (North/South and East/West). The cars are stored in the queue based on their arrival time and processed in the order of arrival.

The state of the intersection can be modeled by keeping track of the number of cars in each queue and the direction of the last car to cross the intersection. This information is used to determine if the next car can cross the intersection or not.

To determine the number of cars that cross the intersection, we use a counter that is incremented each time a car crosses. To ensure that cars that arrive at the same time cross the intersection in the correct order, we process the cars in the queue based on their unique identifier.

## The Solution

The busy intersection problem can be stated as follows: Given two arrays, A and B, of integers, find the set of common elements that appear in both arrays.

The arrays can be of different lengths, and the elements can appear multiple times and in any order. The solution should return a new array that contains the common elements, and its length should be the number of common elements.

The solution should also be efficient, avoiding unnecessary operations and duplications. It should handle edge cases, such as empty arrays and arrays with negative or zero elements.

One possible solution to the busy intersection problem is to use a hash table or dictionary, a data structure that maps keys to values, to store the elements of one of the arrays, and then to check if each element of the other array is in the hash table.

If the element is found, it is added to the result array, and the value in the hash table is updated to avoid duplicates. The solution can be implemented as follows:

## Implementation

The implementation of the busy intersection problem involves the following steps:

Create two separate queues, one for cars traveling North/South and the other for cars traveling East/West.

Read the input and add each car to its respective queue based on its arrival time and direction.

While both queues are not empty, retrieve the car with the earliest arrival time from both queues.

If the last car to cross the intersection was traveling in the opposite direction, allow the first car to cross.

If both cars arrive at the same time, process the car with the lowest identifier first.

Repeat steps 3–5 until both queues are empty.

## The Coding Solution to busy intersection leetcode

The following is our coding solution to busy intersection leetcode