Understanding Unweighted Graph Distances
Return the fewest edges from source to every vertex in an undirected graph. Use -1 for unreachable vertices.
How it works
A FIFO queue discovers vertices in increasing distance, so their first assigned distances are final.
Build an undirected adjacency list and enqueue source at distance zero. Process queued vertices in arrival order. Assign each undiscovered neighbor the current distance plus one before enqueuing.
Try an example
Input: n = 5, edges = [[0, 1], [0, 2], [1, 3]], source = 0
Output: [0, 1, 1, 2, -1]
A FIFO queue discovers vertices in increasing distance, so their first assigned distances are final.
Constraints
- 1–16 vertices numbered 0 through n - 1; at most 48 edges [u, v].
- Source and all edge endpoints must be valid vertices.
- Self-loops and repeated edges are allowed; the source distance is 0.
Use the simulator
Change the input, then choose Visualize input. Use Next and Previous to inspect each decision, or Play to advance automatically. Compare approaches and their complexity. Choose Try yourself to write JavaScript, select My code and Visualize code to inspect its execution, or Run Tests to check results.
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