Find minimum cost in array
Last updated: January 19, 2026
Quick Overview
Given an array of integers representing costs, write a function to find the minimum cost to reach the end of the array, where you can only move to adjacent elements. The function should return the minimum total cost as an integer.
Square/Block
January 19, 202641
15
4,056 solved
Given an array of integers representing costs, write a function to find the minimum cost to reach the end of the array, where you can only move to adjacent elements. The function should return the minimum total cost as an integer.
This coding problem is frequently asked during Phone Screen at Square/Block. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Square/Block expects candidates to write production-quality code, not just solve the puzzle.
What the Interviewer Expects
- Quickly identify the optimal approach and its theoretical basis
- Handle complex algorithm design with multiple interacting components
- Write concise, elegant code under time pressure
- Prove correctness of your approach and discuss alternative solutions
- Optimize beyond the obvious: discuss constant factor improvements
- Address follow-up variations and explain how the solution generalizes
Key Topics to Cover
How to Approach This
- Clarify input constraints and edge cases before writing code.
- Walk through your approach verbally and confirm with the interviewer before coding.
- Start with a brute force solution, then optimize. Mention time and space complexity.
- Test your solution with examples, including edge cases like empty input or duplicates.
- Consider common patterns: sliding window, two pointers, hash map, BFS/DFS, dynamic programming.
Possible Follow-up Questions
- How would you modify your solution to handle streaming input?
- What is the worst-case input for your solution?
- Can you optimize the space complexity of your solution?
- Can you solve this iteratively instead of recursively (or vice versa)?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires us to find the minimum cost to traverse an array, moving only to adjacent elements. This suggests a dynamic programming approach, as we need to consider the cost associated with e...
Approach
- Initialize a list
min_costof the same length as the input array, wheremin_cost[i]will store the minimum cost to reach indexi. - Set
min_cost[0]tocosts[0], since that's the startin...
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