Dijkstra’s Algorithm #1761

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	class Graph {
	constructor() {
	this.adjacencyList = new Map();
	}

	addVertex(vertex) {
	if (!this.adjacencyList.has(vertex)) {
	this.adjacencyList.set(vertex, []);
	}
	}

	addEdge(source, destination, weight) {
	if (!this.adjacencyList.has(source)) {
	this.addVertex(source);
	}
	if (!this.adjacencyList.has(destination)) {
	this.addVertex(destination);
	}
	this.adjacencyList.get(source).push({ node: destination, weight });
	}

	dijkstra(start, end) {
	const distances = {};
	const visited = new Set();
	const priorityQueue = new Map();
	const previous = {};

	// Initialize distances and previous map
	for (let vertex of this.adjacencyList.keys()) {
	distances[vertex] = Infinity;
	previous[vertex] = null;
	}
	distances[start] = 0;
	priorityQueue.set(start, 0);

	while (priorityQueue.size > 0) {
	// Get the node with the smallest distance
	let [currentNode, currentDistance] = [...priorityQueue.entries()].reduce((a, b) => (a[1] < b[1] ? a : b));
	priorityQueue.delete(currentNode);

	// If we reached the destination node, build and return the path
	if (currentNode === end) {
	const path = [];
	while (previous[currentNode]) {
	path.push(currentNode);
	currentNode = previous[currentNode];
	}
	return { path: path.reverse(), distance: distances[end] };
	}

	visited.add(currentNode);

	// Update distances and queue with neighbors
	for (let neighbor of this.adjacencyList.get(currentNode)) {
	if (!visited.has(neighbor.node)) {
	const newDist = currentDistance + neighbor.weight;
	if (newDist < distances[neighbor.node]) {
	distances[neighbor.node] = newDist;
	previous[neighbor.node] = currentNode;
	priorityQueue.set(neighbor.node, newDist);
	}
	}
	}
	}

	return { path: [], distance: Infinity }; // Path not found
	}
	}

	// Example Usage:
	const graph = new Graph();
	graph.addVertex("A");
	graph.addVertex("B");
	graph.addVertex("C");
	graph.addVertex("D");

	graph.addEdge("A", "B", 5);
	graph.addEdge("A", "C", 2);
	graph.addEdge("B", "D", 1);
	graph.addEdge("C", "B", 8);
	graph.addEdge("C", "D", 7);

	const result = graph.dijkstra("A", "D");
	console.log("Shortest path:", result.path);
	console.log("Shortest distance:", result.distance);

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