How do I approach Coding & Algorithms interview questions?

Coding & Algorithms questions require understanding of core concepts and practice. PracHub provides solutions with explanations to help you master coding & algorithms interviews.

What difficulty level is this interview question?

This is a Medium difficulty Coding & Algorithms question, commonly asked during Technical Screen rounds at DoorDash.

What role is this question designed for?

This question is commonly asked for Software Engineer candidates at DoorDash during technical interviews.

Solve string match and DashMart BFS

Last updated: Mar 29, 2026

Quick Overview

This question evaluates proficiency with string algorithms and pattern matching, assessing understanding of substring search complexity and algorithm selection within the algorithms and data structures domain, and is commonly asked to verify efficient low-level text-search implementation and time/space trade-off reasoning at a practical implementation level. The "Dash Mart" grid BFS evaluates graph traversal, state-space modeling, and shortest-path reasoning for multi-target collection tasks within graph algorithms and path-finding, and is commonly asked to measure competence in BFS-based search, state encoding and optimization strategies with a focus on practical algorithmic application and performance considerations.

DoorDash

Aug 4, 2025, 10:55 AM

Software Engineer

Technical Screen

Coding & Algorithms

Question

Implement a string-matching function that returns the first index of a pattern in a text (akin to LeetCode 28 Implement strStr()). 2) “Dash Mart” grid path-finding: given a 2-D map with a start cell, obstacles, and target pickup cells, code a BFS to find the minimum steps to collect all required items and explain follow-up optimizations.

https://leetcode.com/problems/implement-strstr/description/