55 lines
1.3 KiB
JavaScript
55 lines
1.3 KiB
JavaScript
var _ = require("../lodash");
|
|
var PriorityQueue = require("../data/priority-queue");
|
|
|
|
module.exports = dijkstra;
|
|
|
|
var DEFAULT_WEIGHT_FUNC = _.constant(1);
|
|
|
|
function dijkstra(g, source, weightFn, edgeFn) {
|
|
return runDijkstra(g, String(source),
|
|
weightFn || DEFAULT_WEIGHT_FUNC,
|
|
edgeFn || function(v) { return g.outEdges(v); });
|
|
}
|
|
|
|
function runDijkstra(g, source, weightFn, edgeFn) {
|
|
var results = {};
|
|
var pq = new PriorityQueue();
|
|
var v, vEntry;
|
|
|
|
var updateNeighbors = function(edge) {
|
|
var w = edge.v !== v ? edge.v : edge.w;
|
|
var wEntry = results[w];
|
|
var weight = weightFn(edge);
|
|
var distance = vEntry.distance + weight;
|
|
|
|
if (weight < 0) {
|
|
throw new Error("dijkstra does not allow negative edge weights. " +
|
|
"Bad edge: " + edge + " Weight: " + weight);
|
|
}
|
|
|
|
if (distance < wEntry.distance) {
|
|
wEntry.distance = distance;
|
|
wEntry.predecessor = v;
|
|
pq.decrease(w, distance);
|
|
}
|
|
};
|
|
|
|
g.nodes().forEach(function(v) {
|
|
var distance = v === source ? 0 : Number.POSITIVE_INFINITY;
|
|
results[v] = { distance: distance };
|
|
pq.add(v, distance);
|
|
});
|
|
|
|
while (pq.size() > 0) {
|
|
v = pq.removeMin();
|
|
vEntry = results[v];
|
|
if (vEntry.distance === Number.POSITIVE_INFINITY) {
|
|
break;
|
|
}
|
|
|
|
edgeFn(v).forEach(updateNeighbors);
|
|
}
|
|
|
|
return results;
|
|
}
|