Dijkstra's Shortest Path Algortithm Animation in Java

Note: This page is a local copy of one written by Carla Laffra of Pace University, and has been installed with permission.

It describes Dijkstra's well known algorithm to determine the shortest paths in a graph from a given startpoint to any other point. The Dijkstra shortest path algorithm is decribed in many text books, including the very thorough:

• Introduction to Algorithms, Thomas Cormen, Charles Leiserson, and Ronald Rivest, McGraw Hill, 1990.

Interestingly enough, in that book, the algorithm is explained by showing a sample graph where its nodes are colored differently at each step in the algortithm. In that way the authors try to explain the execution of the algorithm, on such a limited medium as paper.

The following Java applet will make the explanation come alive through a user-controlled animation. Each step in the algorithm is explained with a short text shown in a special text area. The applet successfully proves the power of the use of Java for the interactive explanation of (more or less) complex algortithms.

The applet gives the following options:

• show an example graph, or
• let you create your own directed graph with weighted distances between the individual nodes,

Then, you can either

• look at an animation of Dijkstra's algorithm from start to end, or
• walk through the algorithm step by step.

Here is the source code.