Graph traversal refers to the problem of visiting all the nodes in a graph in a particular manner. Tree traversal is a special case of graph traversal. In contrast to tree traversal, in general graph traversal, each node may have to be visited more than once, and a root-like node that connects to all other nodes might not exist.

Depth-first Search

A Depth-first search (DFS) is a technique for traversing a finite undirected graph. DFS visits the child nodes before visiting the sibling nodes, that is, it traverses the depth of the tree before the breadth. That called DFS.

Breadth-first Search

A Breadth-first search (BFS) is another technique for traversing a finite undirected graph. BFS visits the sibling nodes before visiting the child nodes.