What is A* algorithm search?

by

When you want to find the best route between two nodes, you will use an A* algorithm search. Its purpose is to traverse a graph or find a path for this purpose.

A* (pronounced “A-star”) is a widely used search algorithm in the field of artificial intelligence and computer science. It is an informed search algorithm that combines the benefits of both breadth-first and depth-first search strategies while also incorporating heuristic information to guide the search.

Here’s a concise explanation:

  1. Basic Idea: A* aims to find the shortest path from a starting node to a goal node in a weighted graph. It does so by considering both the cost of reaching a node from the start (known as the “g-score”) and an estimate of the cost from the node to the goal (known as the “h-score”).
  2. Heuristic Function (h): A* requires a heuristic function that estimates the cost from any given node to the goal node. This heuristic should be admissible (never overestimate the true cost) and consistent (satisfies the triangle inequality). Common heuristics include Manhattan distance, Euclidean distance, or the number of misplaced tiles in a puzzle.
  3. Cost Evaluation: At each step, A* evaluates the total cost of reaching a node, which is the sum of the cost incurred from the start node (g-score) and the estimated cost to the goal node (h-score). It prioritizes nodes with lower total cost.
  4. Priority Queue: A* utilizes a priority queue to efficiently select the next node for expansion. Nodes are ordered based on their total estimated cost. This ensures that nodes with lower total cost are explored first.
  5. Algorithm Execution: A* continues to expand nodes until it reaches the goal node or exhausts all possible paths. If a goal node is found, the algorithm constructs the shortest path by tracing back from the goal to the start node using the information stored during the search.
  6. Optimality: A* is guaranteed to find the shortest path if the heuristic function is admissible. However, it may not always be the most efficient algorithm in terms of runtime, especially for large graphs or when an inappropriate heuristic is used.

In summary, A* is a versatile and efficient search algorithm that combines the benefits of informed search with heuristic information to find the shortest path in a graph.