115 lines
3.7 KiB
C++
115 lines
3.7 KiB
C++
/*
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* Copyright (C) 2018 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef TNT_UTILS_BINARYTREEARRAY_H
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#define TNT_UTILS_BINARYTREEARRAY_H
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#include <utils/compiler.h>
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#include <type_traits>
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#include <assert.h>
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#include <stddef.h>
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#include <stdint.h>
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namespace utils {
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class BinaryTreeArray {
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// Simple fixed capacity stack
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template<typename TYPE, size_t CAPACITY,
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typename = typename std::enable_if<std::is_pod<TYPE>::value>::type>
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class stack {
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TYPE mElements[CAPACITY];
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size_t mSize = 0;
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public:
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bool empty() const noexcept { return mSize == 0; }
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void push(TYPE const& v) noexcept {
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assert(mSize < CAPACITY);
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mElements[mSize++] = v;
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}
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void pop() noexcept {
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assert(mSize > 0);
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--mSize;
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}
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const TYPE& back() const noexcept {
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return mElements[mSize - 1];
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}
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};
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public:
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static size_t count(size_t height) noexcept { return (1u << height) - 1; }
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static size_t left(size_t i, size_t height) noexcept { return i + 1; }
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static size_t right(size_t i, size_t height) noexcept { return i + (1u << (height - 1)); }
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// this builds the depth-first binary tree array top down (post-order)
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template<typename Leaf, typename Node>
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static void traverse(size_t height, Leaf leaf, Node node) noexcept {
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struct TNode {
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uint32_t index;
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uint32_t col;
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uint32_t height;
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uint32_t next;
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bool isLeaf() const noexcept { return height == 1; }
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size_t left() const noexcept { return BinaryTreeArray::left(index, height); }
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size_t right() const noexcept { return BinaryTreeArray::right(index, height); }
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};
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stack<TNode, 16> stack;
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stack.push(TNode{ 0, 0, (uint32_t)height, (uint32_t)count(height) });
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uint32_t prevLeft = 0;
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uint32_t prevRight = 0;
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uint32_t prevIndex = 0;
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while (!stack.empty()) {
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TNode const* const UTILS_RESTRICT curr = &stack.back();
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const bool isLeaf = curr->isLeaf();
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const uint32_t index = curr->index;
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const uint32_t l = (uint32_t)curr->left();
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const uint32_t r = (uint32_t)curr->right();
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if (prevLeft == index || prevRight == index) {
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if (!isLeaf) {
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// the 'next' node of our left node's right descendants is our right child
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stack.push({ l, 2 * curr->col, curr->height - 1, r });
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}
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} else if (l == prevIndex) {
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if (!isLeaf) {
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// the 'next' node of our right child is our own 'next' sibling
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stack.push({ r, 2 * curr->col + 1, curr->height - 1, curr->next });
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}
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} else {
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if (!isLeaf) {
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node(index, l, r, curr->next);
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} else {
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leaf(index, curr->col, curr->next);
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}
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stack.pop();
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}
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prevLeft = l;
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prevRight = r;
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prevIndex = index;
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}
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}
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};
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} // namespace utils
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#endif //TNT_UTILS_BINARYTREEARRAY_H
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