Is the greedy best-first search algorithm different from the best-first search algorithm?

Question

Is the greedy best-first search algorithm different from the best-first search algorithm?

The wiki page has a separate paragraph about Greedy BFS but it\'s

Answer 1

BFS is an instance of tree search and graph search algorithms in which a node is selected for expansion based on the evaluation function f(n) = g(n) + h(n), where g(n) is length of the path from the root to n and h(n) is an estimate of the length of the path from n to the goal node. In a BFS algorithm, the node with the lowest evaluation (i.e. lowest f(n)) is selected for expansion.

Greedy BFS uses the following evaluation function f(n) = h(n), which is just the heuristic function h(n), which estimates the closeness of n to the goal. Hence, greedy BFS tries to expand the node that is thought to be closest to the goal, without taking into account previously gathered knowledge (i.e. g(n)).

To summarize, the main difference between these (similar) search methods is the evaluation function.

As a side note, the A* algorithm is a best-first search algorithm in which the heuristic function h is an admissible heuristic (i.e. h is always an underestimation of the perfect heuristic function h*, for all n). A* is not a gredy BFS algorithm because its evaluation function is f(n) = g(n) + h(n).