FAANGs ❤️ Linked Lists
Welcome back, Interview Masters! Today’s coding challenge was asked by all FAANG companies in the past six months. Get ready to play with linked lists!
Add Two Numbers Problem
You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order, and each of their nodes contains a single digit. Add the two numbers and return the sum as a linked list.
You may assume the two numbers do not contain any leading zero, except the number 0 itself.
Example 1:
Example 2:
Solve the problem here before reading the solution.
To solve this problem, we will iterate through both linked lists simultaneously, add the corresponding digits and keep track of the carry.
We'll create a dummy node to start the result linked list and a current node to build the result.
At each step:
- Add the values of the current nodes of both lists (if they exist) and the carry.
- Create a new node with the ones digit of the sum and add it to the result linked list.
- Update the carry to be the tens digit of the sum.
- Move to the next nodes in both lists.
After the loop, if there's still a carry, we'll add an additional node to the result.
Uber Design and Architecture
Uber uses microservices architecture. The main services are: Customer Service for handling user accounts, the Driver Service for managing driver information, the Ride Service for matching customers with drivers, and the Payment Service for processing transactions securely using third-party processors like Stripe.
Uber uses WebSockets to track driver and rider location, which allow for real-time updates without overwhelming the servers. They also use clever data structures called Quadtrees to quickly find nearby drivers when a customer requests a ride.
Uber uses techniques like sharding to distribute the database load and caching to speed up frequent requests. For redundancy and fault tolerance, Uber runs multiple copies of each service and uses message queues to make sure important notifications always get delivered.
You can dive into more details here.
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