Interactive DSA and system design

Learn complex engineering ideas by watching them move.

20stepsO(V + E)averageO(V)space

Graphs lab

BFS Level-Order Graph Traversal

Step 1 / 20

FIFO Queue

FrontEmptyBack

Recursion Stack

Empty

Min-Priority Queue

Empty

Visiting Active Node Visited Shortest Path

Animation speed

Space play / pause←→ stepR reset

Current operation

Initialize BFS

We start the Breadth-First Search traversal at Node A. The queue is empty and all nodes are unvisited.

Algorithm state

AStart NodeNoneVisited Order

Select Start Node

Click a node to restart the graph traversal from that starting point.

Complexity notes

O(V + E)averageO(V + E)worstO(V)spaceYesstable

Synced code trace

function BFS(graph, start) {  const queue = [start], visited = new Set([start]);  while (queue.length > 0) {    const curr = queue.shift();    for (const neighbor of graph[curr]) {      if (!visited.has(neighbor)) {        visited.add(neighbor);        queue.push(neighbor);      }    }  }}

Interactive Notes

✓ Notes are saved automatically and persist per step.