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include/ifaces/IIterator.h

@@ -5,7 +5,6 @@
 template <typename T>
 class IIterator {
 public:
-	virtual T& operator*() const = 0;
 	virtual T* operator->() const = 0;
 	virtual operator const T*() const = 0;
 

include/iterators/BFSIterator.h

@@ -0,0 +1,42 @@
+#pragma once
+#include <stack>
+
+#include "iterators/BaseIterator.h"
+
+template <typename T>
+class BFSIterator : public BaseIterator<T> {
+public:
+	explicit BFSIterator(T* ptr) : BaseIterator<T>(ptr) {
+		if (!this->current)
+			return;
+
+		for (auto& it : BaseIterator<T>::current->children())
+			q.push(it.get());
+	}
+
+	IIterator<T>& operator++() override {
+		advance();
+		return *this;
+	}
+
+	virtual size_t level() const {
+		return level_;
+	}
+
+protected:
+	std::queue<T*> q;
+	size_t level_;
+
+	void advance() {
+		if (q.empty()) {
+			this->current = nullptr;
+			return;
+		}
+
+		this->current = q.front();
+		q.pop();
+
+		for (auto& it : this->current->children())
+			q.push(it.get());
+	}
+};

include/iterators/BaseIterator.h

@@ -1,23 +1,43 @@
 #pragma once
+#include <tuple>
 
 #include "ifaces/IIterator.h"
 
 /// \brief Базовый итератор.
 /// \tparam T Тип итерируемого элемента.
 /// Предоставляет базовую реализацию методов для работы с итерируемыми объектами.
+/// Возвращает объект-прокси, мимикрирующий под итерируемый элемент. Позволяет использовать
+/// распаковку структуры для получения уровня элемента в поддереве.
 template <typename T>
 class BaseIterator : public IIterator<T> {
-protected:
-	T* current;
 public:
 	explicit BaseIterator(T* ptr) : current(ptr) {}
 
-	T& operator*() const override { return *current; }
+	struct Proxy {
+		T* e;
+		size_t level;
+
+		T& operator*() const { return *e; }
+		T* operator->() const { return e; }
+	};
+
+	Proxy& operator*() {
+		proxy = Proxy{ current, this->level() };
+		return proxy;
+	}
+
 	T* operator->() const override { return current; }
-	virtual operator const T*() const { return current; }
+	operator const T*() const { return current; }
+	operator T&() const { return *current; }
+	operator T*() const { return current; }
 
 	bool operator!=(const IIterator<T>& other) const override {
 		const T* other_current = other;
 		return current != other_current;
 	}
+
+protected:
+	T* current;
+private:
+	Proxy proxy;
 };

include/iterators/DFSIterator.h

@@ -1,17 +1,18 @@
 #pragma once
 #include <stack>
+#include <iterator>
 
 #include "iterators/BaseIterator.h"
 
 template <typename T>
 class DFSIterator : public BaseIterator<T> {
 public:
-	explicit DFSIterator(T* ptr) : BaseIterator<T>(ptr) {
+	explicit DFSIterator(T* ptr) : BaseIterator<T>(ptr), level_(0) {
 		if (!this->current)
 			return;
 
-		for (auto& it : BaseIterator<T>::current->children())
-			s.push(it.get());
+		for (auto it = BaseIterator<T>::current->children().rbegin(); it != BaseIterator<T>::current->children().rend(); ++it)
+			s.push({it->get(), 1});
 	}
 
 	IIterator<T>& operator++() override {
@@ -22,8 +23,9 @@ public:
 	virtual size_t level() const {
 		return level_;
 	}
+
 protected:
-	std::stack<T*> s;
+	std::stack<std::pair<T*, size_t>> s;
 	size_t level_;
 
 	void advance() {
@@ -32,10 +34,14 @@ protected:
 			return;
 		}
 
-		this->current = s.top();
+		auto [node, lvl] = s.top();
 		s.pop();
 
-		for (auto& it : this->current->children())
-			s.push(it.get());
+		this->current = node;
+		level_ = lvl;
+
+		for (auto it = this->current->children().rbegin();
+		     it != this->current->children().rend(); ++it)
+			s.push({it->get(), lvl + 1});
 	}
 };

include/iterators/Traversal.h

@@ -0,0 +1,22 @@
+#pragma once
+#include <queue>
+
+#include "ifaces/INode.h"
+
+#include "iterators/DFSIterator.h"
+#include "iterators/BFSIterator.h"
+
+template<typename Policy>
+class Traversal {
+	INode* start;
+
+public:
+	explicit Traversal(INode* start) : start(start) {}
+	explicit Traversal(NodePtr start) : start(start.get()) {}
+
+	Policy begin() const { return Policy(start); }
+	Policy end() const { return Policy(nullptr); }
+};
+
+using TraversalDFS = Traversal<DFSIterator<INode>>;
+using TraversalBFS = Traversal<BFSIterator<INode>>;