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A* Algorithm

A* algorithm is an algorithm that is widely used in pathfinding and graph traversal. The algorithm efficiently plots a walkable path between multiple nodes, or points, on the graph. The A* algorithm also has real-world applications. In this example, edges are railroads and h(x) is the great-circle distance (the shortest possible distance on a sphere) to the target. The algorithm is searching for a path between Washington, D.C. and Los Angeles.  The concept of using a heuristic is important in the A* algorithm.

The A* algorithm finding a path of railroads between Washington, D.C. and Los Angeles.

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(Below) A* was invented by researchers working on Shakey the Robot's path planning.

On a map with many obstacles, pathfinding from points AA to BB can be difficult. A robot, for instance, without getting much other direction, will continue until it encounters an obstacle, as in the path-finding example to the left below.

However, the A* algorithm introduces a heuristic into a regular graph-searching algorithm, essentially planning ahead at each step so a more optimal decision is made.