Soumik's Tech Blog

Completeness DFS is not complete, to convince yourself consider that our search start expanding the left subtree of the root for so long path (maybe infinite) when different choice near the root could lead to a solution, now suppose that the left subtree of the root has no solution, and it is unbounded, then the search will continue going deep infinitely, in this case , we say that DFS is not complete. Optimality  Consider the scenario that there is more than one goal node, and our search decided to first expand the left subtree of the root where there is a solution at a very deep level of this left subtree , in the same time the right subtree of the root has a solution near the root, here comes the non-optimality of DFS that it is not guaranteed that the first goal to find is the optimal one, so we conclude that DFS is not optimal. Time Complexity Consider a state space that is identical to that of BFS, with branching factor b, and we start the search from th