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| class PriorityQueue {
constructor(){
this.values = [];
}
enqueue(val, priority) {
this.values.push({val, priority});
this.sort();
};
dequeue() {
return this.values.shift();
};
sort() {
this.values.sort((a, b) => a.priority - b.priority);
};
}
class WeightedGraph {
constructor() {
this.adjacencyList = {};
}
addVertex(vertex){
if(!this.adjacencyList[vertex]) this.adjacencyList[vertex] = [];
}
addEdge(vertex1,vertex2, weight){
this.adjacencyList[vertex1].push({node:vertex2,weight});
this.adjacencyList[vertex2].push({node:vertex1, weight});
}
Dijkstra(start, finish){
const nodes = new PriorityQueue();
const distances = {};
const previous = {};
let path = [] //to return at end
let smallest;
//build up initial state
for(let vertex in this.adjacencyList){
if(vertex === start){
distances[vertex] = 0;
nodes.enqueue(vertex, 0);
} else {
distances[vertex] = Infinity;
nodes.enqueue(vertex, Infinity);
}
previous[vertex] = null;
}
// as long as there is something to visit
while(nodes.values.length){
smallest = nodes.dequeue().val;
if(smallest === finish){
//WE ARE DONE
//BUILD UP PATH TO RETURN AT END
while(previous[smallest]){
path.push(smallest);
smallest = previous[smallest];
}
break;
}
if(smallest || distances[smallest] !== Infinity){
for(let neighbor in this.adjacencyList[smallest]){
//find neighboring node
let nextNode = this.adjacencyList[smallest][neighbor];
//calculate new distance to neighboring node
let candidate = distances[smallest] + nextNode.weight;
let nextNeighbor = nextNode.node;
if(candidate < distances[nextNeighbor]){
//updating new smallest distance to neighbor
distances[nextNeighbor] = candidate;
//updating previous - How we got to neighbor
previous[nextNeighbor] = smallest;
//enqueue in priority queue with new priority
nodes.enqueue(nextNeighbor, candidate);
}
}
}
}
return path.concat(smallest).reverse();
}
}
var graph = new WeightedGraph()
graph.addVertex("A");
graph.addVertex("B");
graph.addVertex("C");
graph.addVertex("D");
graph.addVertex("E");
graph.addVertex("F");
graph.addEdge("A","B", 4);
graph.addEdge("A","C", 2);
graph.addEdge("B","E", 3);
graph.addEdge("C","D", 2);
graph.addEdge("C","F", 4);
graph.addEdge("D","E", 3);
graph.addEdge("D","F", 1);
graph.addEdge("E","F", 1);
graph.Dijkstra("A", "E");
// ["A", "C", "D", "F", "E"]
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