JavaScript Snippet

BFS Traversal Template

Difficulty: Medium

Breadth-first search visits every reachable node in non-decreasing distance from the start, which makes it the right algorithm for shortest-path-in-unweighted-graph, level-order tree traversal, and grid-flood problems. This snippet covers the canonical queue + visited skeleton, the level-by-level form for tree-style problems, and the multi-source variant for problems like 'rotting oranges' where many start points share a frontier.