# Introduction to A

A* (A star) is a search algorithm that is used for finding path from one node to another. So it can be compared with Breadth First Search, or Dijkstraâ€™s algorithm, or Depth First Search, or Best First Search. A* algorithm is widely used in graph search for being better in efficiency and accuracy, where graph pre-processing is not an option.

A* is a an specialization of Best First Search , in which the function of evaluation *f* is define in a particular way.

*f(n) = g(n) + h(n)* is the minimum cost since the initial node to the objectives conditioned to go thought node *n*.

*g(n)* is the minimum cost from the initial node to *n*.

*h(n)* is the minimum cost from *n* to the closest objective to *n*

A* is an informed search algorithm and it always guarantees to find the smallest path (path with minimum cost) in the least possible time (if uses admissible heuristic). So it is both *complete* and *optimal*. The following animation demonstrates A* search-