code: function dfs(n) {
      var children = spanningTree.successors(n);
      for (var c in children) {
        var child = children[c];
        dfs(child);
      }
      if (n !== spanningTree.graph().root) {
        setCutValue(graph, spanningTree, n);
      }
    }
docs: Propagate cut values up the tree.