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Two of the most popular tree traversal algorithms are breadth-first search (BFS) and depth-first search (DFS). Both methods visit all vertices and edges of a graph; however, they are different in the way in which they perform the traversal. This difference determines which of the two algorithms is better suited for a specific purpose.
A major difference between these algorithms is illustrated below:
Other key differences between the two algorithms are:
| BFS | DFS |
|---|---|
| BFS starts traversal from the root node and visits nodes in a level by level manner (i.e., visiting the ones closest to the root first). | DFS starts the traversal from the root node and visits nodes as far as possible from the root node (i.e., depth wise). |
| Usually implemented using a queue data structure. | Usually implemented using a stack data structure. |
| Generally requires more memory than DFS. | Generally requires less memory than BFS. |
| Optimal for finding the shortest distance. | Not optimal for finding the shortest distance. |
| Used for finding the shortest path between two nodes, testing if a graph is bipartite, finding all connected components in a graph, etc. | Used for topological sorting, solving problems that require graph backtracking, detecting cycles in a graph, finding paths between two nodes, etc. |
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