Dijkstra Algorithm Using Javascript.

ashutoshsarangi

Ashutosh Sarangi

Posted on August 23, 2024

Dijkstra Algorithm Using Javascript.

This algorithm is used to calculate minimum shortest distance between cities.

along with the attached article, if you wanted to learn more, I added another enhancement.

  1. I calculated previous path and from there we can get the complete path how it reached there.

const dijkstra = (graph) => {
    const vertex = graph.length;
    const path = new Array(vertex).fill(false);
    const distance = new Array(vertex).fill(Infinity);
    const prev = [-1];
    distance[0] = 0; // source Node

    const getMinDistanceIndex = (path, distance) => {
        let min = Infinity;
        let minIndex = -1;

        for (let j = 0; j< vertex; j++) {
            if (path[j] == false && min > distance[j]) {
                min = distance[j];
                minIndex = j;
            }    
        }    

        return minIndex;
    }

    for (let i = 0; i < vertex; i++) {
        const minDistanceIndex = getMinDistanceIndex(path, distance);
        path[minDistanceIndex] = true;

        for (let j = 0; j< vertex; j++) {
            if (path[j] == false && graph[minDistanceIndex][j] > 0 && distance[minDistanceIndex] + graph[minDistanceIndex][j] < distance[j]) {
                distance[j] = distance[minDistanceIndex] + graph[minDistanceIndex][j];
                prev[j] = minDistanceIndex;
            }
        }
    }

    console.log(path, distance, prev);
}

const graph = [ [ 0, 4, 0, 0, 0, 0, 0, 8, 0 ],
              [ 4, 0, 8, 0, 0, 0, 0, 11, 0 ],
              [ 0, 8, 0, 7, 0, 4, 0, 0, 2 ],
              [ 0, 0, 7, 0, 9, 14, 0, 0, 0],
              [ 0, 0, 0, 9, 0, 10, 0, 0, 0 ],
              [ 0, 0, 4, 14, 10, 0, 2, 0, 0],
              [ 0, 0, 0, 0, 0, 2, 0, 1, 6 ],
              [ 8, 11, 0, 0, 0, 0, 1, 0, 7 ],
              [ 0, 0, 2, 0, 0, 0, 6, 7, 0 ]];

dijkstra(graph);
/*
[true, true, true, true, true, true, true, true, true]
[0, 4, 12, 19, 21, 11, 9,  8, 14]
[-1, 0, 1, 2, 5, 6, 7, 0, 2]
*/
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Feel free to reach out to me if you have any concerns

Reference
https://www.geeksforgeeks.org/dijkstras-shortest-path-algorithm-greedy-algo-7/

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ashutoshsarangi
Ashutosh Sarangi

Posted on August 23, 2024

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