AO* Alogorithm in Artificial Intelligence (A-Star)

May 14, 2023 Ankit Artificial Intelligence Notes In HIndi 0

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A* is a widely used informed search algorithm that efficiently finds the shortest path between a starting node and a goal node in a graph or a weighted grid. It combines elements of both breadth-first search and best-first search algorithms.

Here’s an explanation of the A* algorithm:

  1. Initialization:
    • Assign a cost of zero to the starting node.
    • Assign a heuristic estimate (typically the Manhattan distance or Euclidean distance) from the starting node to the goal node.
    • Maintain an open list and a closed list of nodes.
  2. Search Process:
    • While the open list is not empty, do the following steps:
      • Select the node from the open list with the lowest total cost, which is the sum of the cost to reach that node (known as g(n)) and the heuristic estimate from that node to the goal (known as h(n)).
      • Move the selected node from the open list to the closed list.
      • Generate the successors (neighbors) of the selected node.
      • For each successor, calculate its cost to reach (g(n)) and the heuristic estimate to the goal (h(n)).
      • If the successor is the goal node, the search is complete. Return the path from the start to the goal node.
      • If the successor is already in the closed list with a lower cost, skip it.
      • If the successor is already in the open list with a higher cost, update its cost and parent.
      • If the successor is not in the open list, add it to the open list with the computed cost and parent.
  3. Termination:
    • If the open list becomes empty and no goal node is found, then there is no path from the start node to the goal node. Terminate the search.

The A* algorithm is considered optimal and complete, meaning it guarantees finding the shortest path if it exists, and it will eventually terminate for any given graph. It utilizes an admissible heuristic function, which provides an underestimate of the actual cost from a node to the goal, to guide the search towards the most promising path.

By efficiently exploring the graph while considering both the cost to reach a node and the estimated cost to the goal, the A* algorithm strikes a balance between finding the shortest path and exploring fewer unnecessary nodes, making it a powerful and widely used algorithm in various AI applications such as pathfinding, navigation, and optimization.