08-27-周三_17-09-29

node_modules/graphlib/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);
+
+  var acc = [];
+  var 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); }
+  }
+}