BFS

2 problems using this pattern

About this pattern:

Breadth-first search for shortest path and level-order traversal problems.

Often used with: Graph Queue Shortest Path Tree

Complexity Range

Time Complexity

O(n) (1 problem)
O(V + E) (1 problem)

Space Complexity

O(n) (1 problem)
O(V) (1 problem)

Problems Using BFS

Binary Tree Level Order Traversal

Return the level order traversal of a binary tree.

Medium LeetCode
Time: O(n)
Space: O(n)
Example: [3,9,20,null,null,15,7] → [[3],[9,20],[15,7]]
Tree BFS Queue
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Shortest Path in Unweighted Graph

Find shortest distances from starting node using BFS.

Medium LeetCode
Time: O(V + E)
Space: O(V)
Example: edges=[[0,1],[1,2],[2,3]], start=0 → {0=>0, 1=>1, 2=>2, 3=>3}
Graph BFS Shortest Path
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