Breadth-First Search (BFS) is a fundamental graph traversal algorithm used to explore nodes level by level. Starting from a source node, BFS visits all immediate neighbors first before moving to the next layer. This level-wise exploration makes it extremely useful for solving shortest-path problems in unweighted graphs and for analyzing connectivity in complex systems.
In coding interviews, BFS commonly appears in problems involving graphs, trees, and grids. Many interview questions require you to model the input as a Graph or traverse hierarchical structures such as a Tree. The algorithm typically relies on a Queue to maintain the order of exploration, ensuring nodes are processed in the correct level sequence.
Some common BFS patterns you’ll encounter include:
Because BFS guarantees the shortest number of edges from the starting node, it is frequently used in Shortest Path problems and grid-based challenges. Mastering BFS will help you confidently solve many graph and traversal questions asked in technical interviews.
BFS is primarily used to traverse and explore graphs, making graph representation and adjacency concepts essential.
A queue data structure is used to process nodes in first-in-first-out order during BFS traversal.
BFS is the standard approach for finding the shortest path in unweighted graphs.
Understanding the differences between DFS and BFS helps you choose the right traversal strategy in interviews.
| Status | Title | Video | Leetcode | Solve | Difficulty | Companies | Topics |
|---|---|---|---|---|---|---|---|
| 100. Same Tree | Solve | Easy | Amazon+5 | ||||
| 101. Symmetric Tree | Solve | Easy | Adobe+7 | ||||
| 104. Maximum Depth of Binary Tree | Solve | Easy | Amazon+7 | ||||
| 111. Minimum Depth of Binary Tree | Solve | Easy | Acko+15 | ||||
| 112. Path Sum | Solve | Easy | Amazon+4 | ||||
| 226. Invert Binary Tree | Solve | Easy | Amazon+5 | ||||
| 404. Sum of Left Leaves | Solve | Easy | Adobe+6 | ||||
| 463. Island Perimeter | Solve | Easy | Amazon+2 | ||||
| 530. Minimum Absolute Difference in BST | Solve | Easy | Bloomberg+3 | ||||
| 559. Maximum Depth of N-ary Tree | Solve | Easy | Microsoft | ||||
| 617. Merge Two Binary Trees | Solve | Easy | Amazon+3 | ||||
| 637. Average of Levels in Binary Tree | Solve | Easy | Amazon+2 | ||||
| 653. Two Sum IV - Input is a BST | Solve | Easy | Amazon+1 | ||||
| 733. Flood Fill | Solve | Easy | Adobe+8 | ||||
| 783. Minimum Distance Between BST Nodes | Solve | Easy | Bloomberg+3 | ||||
| 965. Univalued Binary Tree | Solve | Easy | Google | ||||
| 993. Cousins in Binary Tree | Solve | Easy | Amazon+2 | ||||
| 1379. Find a Corresponding Node of a Binary Tree in a Clone of That Tree | Solve | Easy | Amazon | ||||
| 1469. Find All The Lonely Nodes | Solve | Easy | Microsoft | ||||
| 1971. Find if Path Exists in Graph | Solve | Easy | Amazon+2 |
Start Easy, progress to Hard.
Frequently appear alongside Breadth First Search.
Common questions about Breadth First Search.
BFS relies on a queue to keep track of the next nodes to visit. This ensures nodes are processed in the same order they are discovered, enabling level-wise traversal.
Use BFS when you need the shortest path in an unweighted graph or when problems require level-by-level exploration. DFS is typically preferred for deep exploration or recursion-based problems.
BFS is commonly used to solve shortest path, grid traversal, and level-order tree problems. Many interview questions rely on BFS patterns to efficiently explore states or layers.
Breadth-First Search (BFS) is a traversal algorithm that explores nodes level by level from a starting node. It uses a queue to visit neighbors first before moving deeper into the graph.
Practicing a wide range of problems helps you recognize BFS patterns quickly. On TalentD DSA Corner, you can solve 233 Breadth-First Search questions to build strong interview readiness.