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 // Copyright 2014 The Chromium Authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. #include namespace ui { class AXTree; // A class to create all possible trees with up to nodes and the // ids [1...n]. // // There are two parts to the algorithm: // // The tree structure is formed as follows: without loss of generality, // the first node becomes the root and the second node becomes its // child. Thereafter, choose every possible parent for every other node. // // So for node i in (3...n), there are (i - 1) possible choices for its // parent, for a total of (n-1)! (n minus 1 factorial) possible trees. // // The second optional part is the assignment of ids to the nodes in the tree. // There are exactly n! (n factorial) permutations of the sequence 1...n, // and each of these is assigned to every node in every possible tree. // // The total number of trees for a given , including permutations of ids, is // n! * (n-1)! // // n = 2: 2 trees // n = 3: 12 trees // n = 4: 144 trees // n = 5: 2880 trees // // Note that the generator returns all trees with sizes *up to* , which // is a bit larger. // // This grows really fast! Still, it's very helpful for exhaustively testing // tree code on smaller trees at least. class TreeGenerator { public: // Will generate all trees with up to |max_node_count| nodes. // If |permutations| is true, will return every possible permutation of // ids, otherwise the root will always have id 1, and so on. TreeGenerator(int max_node_count, bool permutations); ~TreeGenerator(); int UniqueTreeCount() const; void BuildUniqueTree(int tree_index, AXTree* out_tree) const; private: void BuildUniqueTreeWithSize( int node_count, int tree_index, AXTree* out_tree) const; int max_node_count_; bool permutations_; int total_unique_tree_count_; std::vector unique_tree_count_by_size_; }; } // namespace ui