Add initial version of dijkstra backend cloudron image

helpers/dijkstra_algo.js

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+const Queue = require('./queue');
+const Graph = require('./graph');
+
+function findPathWithDijkstra(cities, roads, startNode, endNode) {
+    const graph = new Graph();
+    
+    // Add cities and roads to graph
+    for (let city of cities) {
+        graph.addNode(city.id)
+    }
+
+    for (let { start_city_id, end_city_id, distance } of roads) {
+        graph.addEdge(start_city_id, end_city_id, distance)
+    }
+    
+    // Dijkstra path search algo
+    let times = {};
+    let backtrace = {};
+    let queue = new Queue();
+
+    times[startNode] = 0;
+
+    graph.nodes.forEach(node => {
+        if (node !== startNode) {
+            times[node] = Infinity
+        }
+    });
+
+    queue.enqueue([startNode, 0]);
+
+    while (queue.size()) {
+        let shortestStep = queue.dequeue();
+        let currentNode = shortestStep[0];   
+        graph.adjacencyList[currentNode].forEach(neighbor => {
+            let time = times[currentNode] + neighbor.distance;
+        
+            if (time < times[neighbor.node]) {
+                times[neighbor.node] = time;
+                backtrace[neighbor.node] = currentNode;
+                queue.enqueue([neighbor.node, time]);
+            }
+        });
+    }
+
+    let path = [endNode];
+    let lastStep = endNode;  while(lastStep !== startNode) {
+        path.unshift(backtrace[lastStep])
+        lastStep = backtrace[lastStep]
+    } 
+    
+    // return `Path is ${path} and time is ${times[endNode]}`
+    return {path, distance: times[endNode]}
+}
+
+module.exports = findPathWithDijkstra;

helpers/graph.js

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+class Graph {
+    constructor() {
+        this.nodes = [];
+        this.adjacencyList = {};
+    }
+
+    addNode(node) {
+        this.nodes.push(node); 
+        this.adjacencyList[node] = [];
+    }
+
+    addEdge(node1, node2, distance) {
+        this.adjacencyList[node1].push({node:node2, distance});
+        this.adjacencyList[node2].push({node:node1, distance});
+    }
+}
+
+module.exports = Graph;

helpers/queue.js

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+class Queue {
+    constructor() {
+    this.store = [];
+    }
+
+    size() {
+        return this.store.length
+    }
+
+    enqueue(node) {
+        this.store.push(node);
+    }
+
+    dequeue() {
+        if (this.size() > 0) {
+            return this.store.shift();
+        }
+    } 
+}
+
+module.exports = Queue;