This is a premium problem. We're working on making it available for free soon.
Explore Free ProblemsSolutions for this premium problem will be available for free soon.
Browse Free ProblemsWatch expert explanations and walkthroughs
Practice problems asked by these companies to ace your technical interviews.
Explore More ProblemsJot down your thoughts, approach, and key learnings
Running BFS from each building ensures we compute distances efficiently and only once per building. If we started BFS from every empty cell, the algorithm would become significantly slower because the number of empty cells can be much larger than the number of buildings.
Yes, this problem is considered a classic hard-level grid BFS question and has appeared in interviews at large tech companies. It tests understanding of BFS traversal, grid optimization, and how to aggregate distances across multiple sources.
A queue is the key data structure used for BFS traversal of the grid. Additionally, matrices or 2D arrays are used to store cumulative distances and the number of buildings that can reach each cell.
The optimal approach uses Breadth-First Search (BFS) starting from each building. During each BFS, distances to reachable empty cells are accumulated and a reach counter is updated. After processing all buildings, the cell reachable from every building with the minimum total distance is chosen.