Introduction

This pattern is based on the Breadth First Search (BFS) technique to traverse a tree.

Any problem involving the traversal of a tree in a level-by-level order can be efficiently solved using this approach. We will use a Queue to keep track of all the nodes of a level before we jump onto the next level. This also means that the space complexity of the algorithm will be $O(W)$, where ‘W’ is the maximum number of nodes on any level.

Let’s jump onto our first problem to understand this pattern.