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A Star Algo

Posted on:November 24, 2023 at 09:54 AM

A* Algorithm: Introduction and Overview

The A* algorithm is a widely-used heuristic search algorithm in artificial intelligence, graph theory, and computer science. It is particularly known for its applications in pathfinding and navigation problems in fields such as video games, robotics, and virtual environments. This post will provide an overview of the A* algorithm and walk you through its mathematical foundations.


The A* algorithm was first introduced by Peter Hart, Nilsson Sten, and Erik Bergen in 1968, as a modification to Dijkstra’s shortest path algorithm. The main idea behind the A* algorithm is to find the optimal solution for a given problem while minimizing computational complexity.

Overview of the Algorithm

The A* algorithm operates on a graph, where each node represents a possible location or state in the problem domain, and edges represent transitions between these locations. The objective of the A* algorithm is to find the optimal path from a starting point (source) to an end point (destination) while considering a heuristic function to estimate the remaining cost of reaching the destination from any intermediate node.

Mathematical Foundation

The A* algorithm is based on a combination of Dijkstra’s shortest path algorithm and a greedy search strategy. The key component of the A* algorithm is its priority queue, which stores nodes based on their estimated total cost (g-score) plus a heuristic function (h-score).

  1. Initialization: Set the source node as the current node and initialize the g-scores for all nodes to infinity except the source node, which has a g-score of 0. Initialize h-scores using an admissible heuristic function.
  2. Priority Queue: The priority queue stores nodes based on their f-score (g-score + h-score). The f-score is used to determine the order in which nodes are expanded, with lower f-scores being processed first.
  3. Node Expansion: For each node in the priority queue, calculate its neighbors and check if they have not been visited or have a lower g-score. If so, update the neighbor’s g-score and h-score, add it to the priority queue, and mark the current node as visited.
  4. Stop Condition: If the destination node is visited, return the optimal path by backtracking from the destination to the source using the parent pointers stored during the expansion process. Otherwise, repeat steps 3-4 until either a timeout or maximum number of nodes in the priority queue is reached.


The A* algorithm is a powerful tool for solving complex problems involving pathfinding and navigation in various domains. Its ability to provide near-optimal solutions while maintaining computational efficiency makes it a popular choice among researchers and developers alike. By understanding the mathematical foundations of the A* algorithm, you can gain insights into its inner workings and apply this knowledge to your own projects or research endeavors.