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dijkstras.js
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dijkstras.js
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/**
* Basic priority queue implementation. If a better priority queue is wanted/needed,
* this code works with the implementation in google's closure library (https://code.google.com/p/closure-library/).
* Use goog.require('goog.structs.PriorityQueue'); and new goog.structs.PriorityQueue()
*/
function PriorityQueue() {
this._nodes = [];
this.enqueue = (priority, key) => {
this._nodes.push({
key: key,
priority: priority
});
this.sort();
};
this.dequeue = () => this._nodes.shift().key;
this.sort = () => this._nodes.sort((a, b) => a.priority - b.priority);
this.isEmpty = () => !this._nodes.length;
}
/**
* Pathfinding starts here
*/
function Graph() {
var INFINITY = 1 / 0;
this.vertices = {};
this.addVertex = function (name, edges) {
this.vertices[name] = edges;
};
this.getVertex = function (name) {
return this.vertices[name];
};
this.shortestPath = function (start, finish) {
var nodes = new PriorityQueue();
var distances = {};
var previous = {};
var path = [];
for (let vertex in this.vertices) {
if (vertex === start) {
distances[vertex] = 0;
nodes.enqueue(0, vertex);
} else {
distances[vertex] = INFINITY;
nodes.enqueue(INFINITY, vertex);
}
previous[vertex] = null;
}
while (!nodes.isEmpty()) {
let smallest = nodes.dequeue();
if (smallest === finish) {
path = [];
while (previous[smallest]) {
path.push(smallest);
smallest = previous[smallest];
}
break;
}
if (!smallest || distances[smallest] === INFINITY) continue;
for (let neighbor in this.vertices[smallest]) {
let alt = distances[smallest] + this.vertices[smallest][neighbor];
if (alt < distances[neighbor]) {
distances[neighbor] = alt;
previous[neighbor] = smallest;
nodes.enqueue(alt, neighbor);
}
}
}
return path.concat(start).reverse();
};
this.calcDistance = function(path) {
let distance = 0;
for (let i = 0; i < path.length; i++) {
let nextVertexName = path[i + 1];
if (!nextVertexName) break;
let vertexName = path[i];
distance += this.getVertex(vertexName)[nextVertexName];
}
return distance;
};
}
module.exports = {
priorityQueue: PriorityQueue,
graph: Graph,
createPriorityQueue: () => new PriorityQueue(),
createGraph: () => new Graph(),
};