08-27-周三_17-09-29

node_modules/graphlib/lib/alg/dijkstra.js

@@ -0,0 +1,54 @@
+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;
+}