DoorDash Frontend Engineer Interview Questions

DoorDash wants to create bundled promotions that maximize customer engagement while ensuring profit margins. Given an array of integers products representing the price of each product and an integer target, find all combinations of products that sum up to exactly target.Function Signature:
python
combinationSum(products: List[int], target: int) -> List[List[int]]
Example 1:
Input: products = [2, 3, 6, 7], target = 7
Output: [[7], [2, 2, 3]]
Explanation: The combinations that yield 7 are the combinations of products 7 and the numbers 2 and 3 in different quantities.Constraints:
- 1 <= products.length <= 30
- 2 <= products[i] <= 40
- 1 <= target <= 500

DoorDash needs to optimize the delivery routes for drivers by calculating the maximum distance they can cover within a given time frame.
Given an array orders where each entry represents the distance of an order from the restaurant and an integer Time which represents the maximum time available, calculate the maximum total distance of orders that can be completed within that time. The distance for each order is defined as distance[i] = time[i] * speed[i] where speed can be considered constant.Function Signature:
python
maxDeliveryDistance(orders: List[int], Time: int) -> int
Example 1:
Input: orders = [1, 2, 3, 4, 5], Time = 7
Output: 12
Explanation: The driver can complete orders 3, 4, and 5 within the time limit, accounting for the maximum distance covered.Constraints:
- 1 <= orders.length <= 1000
- 1 <= orders[i] <= 100
- 1 <= Time <= 1000

To manage rapid UI events effectively, DoorDash needs a debounced EventEmitter that prevents triggering events excessively during high-frequency interactions, such as clicks or scrolls.Class Definition:
python
class EventEmitter:
def __init__(self):
# Initialize your EventEmitter here.
pass

def on(self, event: str, listener: Callable) -> None:
# Add an event listener.
pass

def emit(self, event: str, *args) -> None:
# Trigger an event.
pass

def debounce(self, delay: int) -> Callable:
# Return debounced version of the listener.
pass
Example 1:
Input: emitter = EventEmitter()
emitter.on('event', listenerFunction)
debouncedListener = emitter.debounce(300)
debouncedListener()
Output: Will trigger the listener only if no other calls occur within 300ms.Constraints:
- Maximum of 1000 events.

In order to enhance the user experience on DoorDash, we need to create a client-side router that manages different pages and their states within a single-page application (SPA) framework.Class Definition:
python
class Router:
def __init__(self):
# Initialize your router here.
pass

def add_route(self, path: str, component: Callable) -> None:
# Add a route to the router.
pass

def navigate(self, path: str) -> None:
# Navigate to a specified path.
pass

def get_current_route(self) -> str:
# Get the current route being displayed.
pass
Example 1:
Input: router = Router()
router.add_route('/restaurants', RestaurantsPage)
router.navigate('/restaurants')
Output: Current route: /restaurantsConstraints:
- Maximum of 50 routes.
- Each route path must be unique.