Кастомный итератор по древовидной структуре.

Author: gusenov

README.md

@@ -137,6 +137,10 @@
 
 - [std::unordered_map при своём разрушении не вызывает деструктор для значений хранящихся по указателю](std/collections/map/unordered-map-el-dtor)
 
+### Итераторы
+
+- [Кастомный итератор по древовидной структуре](it/tree-iter)
+
 ## Потоки данных
 
 - [Потоки из стандартной библиотеки](stream/streams)

it/tree-iter/.gitignore

@@ -0,0 +1,54 @@
+# ---------------------------------------------------------------------------
+# https://github.com/github/gitignore/blob/master/Global/Linux.gitignore
+
+*~
+
+# temporary files which can be created if a process still has a handle open of a deleted file
+.fuse_hidden*
+
+# KDE directory preferences
+.directory
+
+# Linux trash folder which might appear on any partition or disk
+.Trash-*
+
+# .nfs files are created when an open file is removed but is still being accessed
+.nfs*
+
+# ---------------------------------------------------------------------------
+# https://github.com/github/gitignore/blob/master/C++.gitignore
+
+# Prerequisites
+*.d
+
+# Compiled Object files
+*.slo
+*.lo
+*.o
+*.obj
+
+# Precompiled Headers
+*.gch
+*.pch
+
+# Compiled Dynamic libraries
+*.so
+*.dylib
+*.dll
+
+# Fortran module files
+*.mod
+*.smod
+
+# Compiled Static libraries
+*.lai
+*.la
+*.a
+*.lib
+
+# Executables
+*.exe
+*.out
+*.app
+
+# ---------------------------------------------------------------------------

it/tree-iter/REFERENCES.md

@@ -0,0 +1,36 @@
+- [итераторы - Класс-итератор c++ - Stack Overflow на русском](https://ru.stackoverflow.com/questions/717528/%D0%9A%D0%BB%D0%B0%D1%81%D1%81-%D0%B8%D1%82%D0%B5%D1%80%D0%B0%D1%82%D0%BE%D1%80-c)
+
+- [std::iterator is deprecated: Why, What It Was, and What to Use Instead - Fluent C++](https://www.fluentcpp.com/2018/05/08/std-iterator-deprecated/)
+- [Делаем свой итератор / Хабр](https://habr.com/ru/post/265491/)
+- [Недооценённые итераторы / Хабр](https://habr.com/ru/post/122283/)
+- [C++ iterator example (and an iterable range) – Andy Balaam's Blog](https://www.artificialworlds.net/blog/2017/05/11/c-iterator-example-and-an-iterable-range/)
+- [Jacek's C++ Blog · Wrapping Algorithms into Iterators](https://blog.galowicz.de/2016/09/04/algorithms_in_iterators/)
+- [Defining a custom iterator in C++ | Lorenzo Toso](https://lorenzotoso.wordpress.com/2016/01/13/defining-a-custom-iterator-in-c/)
+- [Defining C++ Iterators](http://users.cs.northwestern.edu/~riesbeck/programming/c++/stl-iterator-define.html)
+- [Generating Sequences | Just Software Solutions - Custom Software Development](https://www.justsoftwaresolutions.co.uk/cplusplus/generating_sequences.html)
+
+- [<iterator> - C++ Reference](http://www.cplusplus.com/reference/iterator/)
+
+- [C++ | Итераторы](https://metanit.com/cpp/tutorial/7.3.php)
+- [Урок №198. Итераторы STL | Уроки С++ - Ravesli](https://ravesli.com/urok-198-iteratory-stl/)
+
+- [c++ - How to implement operator-> for iterator type? - Stack Overflow](https://stackoverflow.com/questions/9007775/how-to-implement-operator-for-iterator-type)
+- [c++ - How to implement operator-> for an iterator that constructs its values on-demand? - Stack Overflow](https://stackoverflow.com/questions/27582845/how-to-implement-operator-for-an-iterator-that-constructs-its-values-on-demand)
+
+- [перегрузка оператора -> (стрелка :) ) - C/C++ - RSDN](https://rsdn.org/forum/cpp/2705999.all)
+- [Overloading member access operators ->, .* (C++) - Stack Overflow](https://stackoverflow.com/questions/8777845/overloading-member-access-operators-c)
+
+- [c++ - Writing a custom iterator -- what to do if you're at the end of the array? - Stack Overflow](https://stackoverflow.com/questions/2706539/writing-a-custom-iterator-what-to-do-if-youre-at-the-end-of-the-array)
+
+- [std::ptrdiff_t - cppreference.com](https://en.cppreference.com/w/cpp/types/ptrdiff_t)
+
+- [Implementing an iterator over binary (or arbitrary) tree using C++ 11 - Stack Overflow](https://stackoverflow.com/questions/12684191/implementing-an-iterator-over-binary-or-arbitrary-tree-using-c-11)
+
+- [c++ - How to correctly implement custom iterators and const_iterators? - Stack Overflow](https://stackoverflow.com/questions/3582608/how-to-correctly-implement-custom-iterators-and-const-iterators)
+
+- [Sample C++/STL custom iterator](https://gist.github.com/jeetsukumaran/307264)
+- [qt/qlist.h at master · radekp/qt](https://github.com/radekp/qt/blob/master/src/corelib/tools/qlist.h#L162)
+
+- [Example of STL compatible custom containers + iterators : cpp](https://www.reddit.com/r/cpp/comments/9nz3xl/example_of_stl_compatible_custom_containers/)
+
+- [Iterator Facade - 1.68.0](https://www.boost.org/doc/libs/1_68_0/libs/iterator/doc/iterator_facade.html)

it/tree-iter/TreeNode.cc

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+#include "TreeNode.h"
+#include "TreeNodeIterator.h"
+
+TreeNode::TreeNode(int value) {
+    value_ = value;
+}
+
+int TreeNode::GetValue() const {
+    return value_;
+}
+
+void TreeNode::AddChildNode(TreeNode *node) {
+    children_.push_back(node);
+}
+
+size_t TreeNode::GetChildrenCount() const {
+    return children_.size();
+}
+
+TreeNode * TreeNode::GetChildAtIndex(size_t index) const {
+    return children_.at(index);
+}
+
+TreeNodeIterator TreeNode::begin() {
+    return TreeNodeIterator(this);
+}
+
+TreeNodeIterator TreeNode::end() {
+    TreeNode *node = this;
+    while (node->GetChildrenCount()) {
+        node = node->GetChildAtIndex(node->GetChildrenCount() - 1);
+    }
+    return TreeNodeIterator(nullptr);
+}

it/tree-iter/TreeNode.h

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+#ifndef TreeNode_h
+#define TreeNode_h
+
+#include <vector>
+
+
+class TreeNodeIterator;
+class TreeNode {
+    std::vector<TreeNode *> children_;
+    int value_ = -1;
+public:
+    explicit TreeNode(int value);
+    ~TreeNode() = default;
+    int GetValue() const;
+    void AddChildNode(TreeNode *node);
+    size_t GetChildrenCount() const;
+    TreeNode * GetChildAtIndex(size_t index) const;
+    TreeNodeIterator begin();
+    TreeNodeIterator end();
+};
+
+#endif /* TreeNode_h */

it/tree-iter/TreeNodeIterator.h

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+#ifndef TreeNodeIterator_h
+#define TreeNodeIterator_h
+
+#include <iostream>
+#include <stack>
+#include "TreeNode.h"
+
+
+class TreeNodeIterator {
+    std::stack<TreeNode *> stack_;
+
+public:
+    // Обязательными являются первые два параметра:
+
+    // Тип итератора:
+    typedef std::input_iterator_tag iterator_category;
+    // Тип выбирается из следующих типов:
+    //   input_iterator_tag
+    //     Должен поддерживать префиксную форму инкремента, оператор !=,
+    //     оператор * и оператор ->. Понадобится конструктор и конструктор
+    //     копирования.
+    //   output_iterator_tag
+    //   forward_iterator_tag
+    //   bidirectional_iterator_tag
+    //   random_access_iterator_tag
+
+    // Тип значения которое хранится и возвращается операторами * и ->:
+    typedef TreeNode value_type;
+
+    // Тип который может описывать растояние между итераторами:
+    typedef std::ptrdiff_t difference_type;
+
+    // Тип указателя на значение:
+    typedef TreeNode *pointer;
+
+    // Тип ссылки на значения:
+    typedef TreeNode &reference;
+
+
+    explicit TreeNodeIterator(TreeNode *value = nullptr) {
+        if (value)
+            stack_.push(value);
+    }
+
+    // TreeNode * operator*() const {
+    //     return !stack_.empty() ? stack_.top() : nullptr;
+    // }
+
+    typename TreeNodeIterator::reference operator*() const {
+        TreeNode *node = nullptr;
+        if (!stack_.empty()) {
+            node = stack_.top();
+        }
+        return *node;
+    }
+
+    TreeNode * operator->() const {
+        return !stack_.empty() ? stack_.top() : nullptr;
+    }
+
+
+    //  Хорошая практика добавлять поддержку != и == вместе:
+
+    bool operator==(TreeNodeIterator const &other) const {
+        if (stack_.empty() || other.stack_.empty())
+            return stack_.empty() && other.stack_.empty();
+
+        return stack_.top() == other.stack_.top();
+    }
+
+    bool operator!=(TreeNodeIterator const &other) const {
+        return !(*this == other);
+    }
+
+
+    TreeNodeIterator & operator++() {
+        if (!stack_.empty()) {
+            TreeNode *node = stack_.top();
+            stack_.pop();
+            for (int i = node->GetChildrenCount() - 1; i >= 0; --i)
+                stack_.push(node->GetChildAtIndex(i));
+        }
+        return *this;
+    }
+
+};
+
+#endif /* TreeNodeIterator_h */

it/tree-iter/main.cc

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+#include <iostream>
+#include <cstdlib>
+
+#include "TreeNode.h"
+#include "TreeNodeIterator.h"
+
+
+void test1() {
+    std::vector<TreeNode> v = { };
+    auto iter = v.begin();
+    std::cout << (*iter).GetValue() << std::endl;
+    ++iter;
+    while(iter != v.end()) {
+        std::cout << iter->GetValue() << std::endl;
+        ++iter;
+    }
+    exit(0);
+}
+
+int main(int argc, const char * argv[]) {
+    // test1();
+
+    TreeNode root(0);
+
+    TreeNode n1(1);
+    TreeNode n11(11);
+    TreeNode n12(12);
+    n1.AddChildNode(&n11);
+    n1.AddChildNode(&n12);
+
+    TreeNode n2(2);
+    TreeNode n21(21);
+    TreeNode n22(22);
+    n2.AddChildNode(&n21);
+    n2.AddChildNode(&n22);
+
+    TreeNode n3(3);
+    TreeNode n31(31);
+    TreeNode n32(32);
+    n3.AddChildNode(&n31);
+    n3.AddChildNode(&n32);
+
+    root.AddChildNode(&n1);
+    root.AddChildNode(&n2);
+    root.AddChildNode(&n3);
+
+    auto iter = root.begin();
+    std::cout << (*iter).GetValue() << std::endl;
+    ++iter;
+
+    while(iter != root.end()) {
+        std::cout << iter->GetValue() << std::endl;
+        ++iter;
+    }
+
+    return EXIT_SUCCESS;
+}

it/tree-iter/run.sh

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+#!/bin/bash
+
+EXE_FILE="./program.out"
+
+[ -f "$EXE_FILE" ] && rm "$EXE_FILE"
+
+clang++ --std=c++17 `find . -maxdepth 1 -name "*.cc" | tr '\n' ' '` -o "$EXE_FILE" && "$EXE_FILE"