DFS is more suitable for game or puzzle problems. It uses a Queue data structure which follows first in first out. We make a decision, then explore all paths through this decision. See your article appearing on the GeeksforGeeks main page and help other Geeks. A vertex represents a point in the graph, and can be identified by it's key. BFS considers all neighbors first and therefore not suitable for decision making trees used in games or puzzles. To express this algorithm in code, we'll create a minimal queue implementation: We can then create a function for BFS traversal: If you feel like you've got the hang of BFS and DFS, let's test your knowledge! Please write to us at contribute@geeksforgeeks.org to report any issue with the above content. If we consider the same example graph used in the last example, we can picture the traversal order and the queue as follows: Every time we traverse a node, we enqueue its child nodes, and then move on to the next node in the queue. This can be best described by an illustration. Consider this sample graph: If we start with Node 1, we traverse each child node, and if the child node has any children, we traverse those first before going to a sister node: Note that nodes 3 and 4 are never visited since they're disconnected from the starting node. With respect to node 1, node 6 is three levels deep, where are node 9 is only two levels deep. Step 1) You have a graph of seven numbers ranging from 0 – 6. DFS is known as the Depth First Search Algorithm which provides the steps to traverse each and every node of a graph without repeating any node. It starts at the tree root (or some arbitrary node of a graph, sometimes referred to as a ‘search key’) and explores the neighbor nodes first, … Assuming we use BFS, which node would be visited first for this graph? Common Graph Algorithms. Please use ide.geeksforgeeks.org, generate link and share the link here. In BFS, one vertex is selected at a time when it is visited and marked then its adjacent are visited and stored in the queue. Ex-. It is slower than DFS. And if this decision leads to win situation, we stop. This is a bit more complex than depth first search since we have to keep track of the child nodes that we want to traverse later. BFS can be used to find single source shortest path in an unweighted graph, because in BFS, we reach a vertex with minimum number of edges from a source vertex. 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