BFS on array
Last updated: November 21, 2025
Quick Overview
Implement a Breadth-First Search (BFS) algorithm to traverse a given array, where each element represents the maximum number of steps that can be taken forward from that position. Your task is to determine the minimum number of jumps required to reach the last index of the array, or return -1 if it is not possible. The input will be an array of non-negative integers, and the output should be an integer representing the minimum jumps.
Robinhood
November 21, 202525
14
4,231 solved
Implement a Breadth-First Search (BFS) algorithm to traverse a given array, where each element represents the maximum number of steps that can be taken forward from that position. Your task is to determine the minimum number of jumps required to reach the last index of the array, or return -1 if it is not possible. The input will be an array of non-negative integers, and the output should be an integer representing the minimum jumps.
This coding problem is frequently asked during Phone Screen at Robinhood. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Robinhood 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
- What happens if the input contains duplicates?
- How would your solution change if the input was sorted?
- What if the input doesn't fit in memory?
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Problem Analysis
This problem can be approached using the Breadth-First Search (BFS) algorithm. Each position in the array can be seen as a node in a graph, where edges lead to subsequent indices that can be reach...
Approach
- Initialize a queue: Start with the first index (0) in the queue and maintain a count of jumps (initially 0).
- BFS Loop: While the queue is not empty:
- Dequeue the current index and th...
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