08-27-周三_17-09-29

node_modules/graphlibrary/lib/alg/dijkstra.js

@@ -0,0 +1,54 @@
+const _ = require('../lodash')
+const 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) {
+  const results = {}
+  const pq = new PriorityQueue()
+  let v, vEntry
+
+  var updateNeighbors = function (edge) {
+    const w = edge.v !== v ? edge.v : edge.w
+    const wEntry = results[w]
+    const weight = weightFn(edge)
+    const 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
+}