08-27-周三_17-09-29

node_modules/graphlibrary/lib/alg/dfs.js

@@ -0,0 +1,42 @@
+var _ = require('../lodash')
+
+module.exports = dfs
+
+/*
+ * A helper that preforms a pre- or post-order traversal on the input graph
+ * and returns the nodes in the order they were visited. If the graph is
+ * undirected then this algorithm will navigate using neighbors. If the graph
+ * is directed then this algorithm will navigate using successors.
+ *
+ * Order must be one of "pre" or "post".
+ */
+function dfs (g, vs, order) {
+  if (!_.isArray(vs)) {
+    vs = [vs]
+  }
+
+  var navigation = (g.isDirected() ? g.successors : g.neighbors).bind(g)
+
+  const acc = []
+  const visited = {}
+  _.each(vs, function (v) {
+    if (!g.hasNode(v)) {
+      throw new Error('Graph does not have node: ' + v)
+    }
+
+    doDfs(g, v, order === 'post', visited, navigation, acc)
+  })
+  return acc
+}
+
+function doDfs (g, v, postorder, visited, navigation, acc) {
+  if (!_.has(visited, v)) {
+    visited[v] = true
+
+    if (!postorder) { acc.push(v) }
+    _.each(navigation(v), function (w) {
+      doDfs(g, w, postorder, visited, navigation, acc)
+    })
+    if (postorder) { acc.push(v) }
+  }
+}