DoorDash Software Engineer Coding & Algorithms Interview Questions
Practice 57 real Coding & Algorithms interview questions for Software Engineer roles at DoorDash.
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Validate a Shopping Cart
You are building the cart validation logic for a food-delivery application. Implement a function validateCart(cart, catalog) that checks whether a cus...
Implement Timeout Refund Workflow
You are given a skeleton workflow engine for order processing. A workflow is a directed graph of nodes. Each node receives an OrderContext and returns...
Calculate Driver Payments
Build a payout calculator for a delivery platform. You are given: - A list of delivery records. Each record has delivery_id, driver_id, start_time, en...
Implement dasher active-time calculator
Implement a function that, given a dasherId, a local pay-period interval [startLocalDateTime, endLocalDateTime), and a list of order events of the for...
Find longest common ordered restaurant list
You have two delivery drivers who each have a pickup plan represented as a list of restaurant IDs (strings). Because there is only one car, the combin...
Implement consistent hashing ring
Implement consistent hashing ring Implement consistent hashing for routing keys to servers. Provide APIs addNode(nodeId, weight), removeNode(nodeId), ...
Debug using logs and allocate tasks
You inherit a service where unit tests pass locally, but production logs show intermittent errors. Without a debugger, outline a step-by-step debuggin...
Maximize Chef Assignment Profit
You are given three integer arrays: - chefSkill[i]: the skill level of the i-th chef. - dishDifficulty[j]: the difficulty level required to cook the j...
Calculate Daily Driver Pay
You are given a one-day event log for a delivery driver. Each input record is a JSON event with fields such as order_id, event_type, timestamp, and ba...
Compute dasher pay with peak-hour query
Problem: Dasher pay calculation + peak-hour earnings You are given historical delivery records for a driver (“dasher”). Each record contains: - start_...
Compute cart total with best promotion
Assume you are implementing a checkout price calculator for an online shopping cart. You are given: - A list of items in the cart. Each item has: - ...
Implement round-robin load balancer
Implement a load balancer that distributes incoming requests across N backend servers in strict round-robin order. Requirements: ( 1) Support addServe...
Can two names match with ≤2 swaps?
You are given two restaurant names represented as strings s and t of equal length (same character set, case-sensitive). In one operation, you may swap...
Design hierarchical path store with create/set/get/remove
Design a hierarchical key-value path store supporting four operations on UNIX-style absolute paths (e.g., "/a/b"). Implement: 1) create(path, value): ...
Compute Courier Delivery Pay
A delivery platform has a service that can return all orders delivered by a courier. You are given: - courierId: the courier's identifier. - ratePerMi...
Compute Differences Between Catalog Trees
You are given two rooted catalog trees. Each node has a unique string key among its siblings and an associated value. Compare the two trees and return...
Compute earliest arrival in time-grid
Question LeetCode 778. Swim in Rising Water – Given an n x n integer grid where grid[i][j] is the earliest time you can enter the cell, starting from ...
Implement string matching with follow-up
Question Given a text T and a pattern P, implement a function firstIndex(T, P) that returns the starting index of the first occurrence of P in T, or -...
Compute delivery times on a grid
You are given a 2D grid with cells marked as 'M' (warehouses), 'C' (customers), 'X' (obstacles), and '.' (roads). You can move up, down, left, or righ...
Compute nearest-exit distances in a grid
Compute nearest-exit distances in a grid You are given a 2D grid representing a building floor with three cell types: -1 for walls, 0 for exits, and a...