fix: revert

Author: realstealthninja

data_structures/stack.hpp

@@ -0,0 +1,80 @@
+/**
+ * @file
+ * @author danghai
+ * @author [Piotr Idzik](https://github.com/vil02)
+ * @brief  This class specifies the basic operation on a stack as a linked list
+ **/
+#ifndef DATA_STRUCTURES_STACK_HPP_
+#define DATA_STRUCTURES_STACK_HPP_
+
+#include <stdexcept>  /// for std::invalid_argument
+
+#include "node.hpp"  /// for Node
+
+/** Definition of the stack class
+ * \tparam value_type type of data nodes of the linked list in the stack should
+ * contain
+ */
+template <class ValueType>
+class stack {
+ public:
+    using value_type = ValueType;
+
+    /** Show stack */
+    void display() const {
+        std::cout << "Top --> ";
+        display_all(this->stackTop.get());
+        std::cout << '\n';
+        std::cout << "Size of stack: " << size << std::endl;
+    }
+
+    std::vector<value_type> toVector() const {
+        return push_all_to_vector(this->stackTop.get(), this->size);
+    }
+
+ private:
+    void ensureNotEmpty() const {
+        if (isEmptyStack()) {
+            throw std::invalid_argument("Stack is empty.");
+        }
+    }
+
+ public:
+    /** Determine whether the stack is empty */
+    bool isEmptyStack() const { return (stackTop == nullptr); }
+
+    /** Add new item to the stack */
+    void push(const value_type& item) {
+        auto newNode = std::make_shared<Node<value_type>>();
+        newNode->data = item;
+        newNode->next = stackTop;
+        stackTop = newNode;
+        size++;
+    }
+
+    /** Return the top element of the stack */
+    value_type top() const {
+        ensureNotEmpty();
+        return stackTop->data;
+    }
+
+    /** Remove the top element of the stack */
+    void pop() {
+        ensureNotEmpty();
+        stackTop = stackTop->next;
+        size--;
+    }
+
+    /** Clear stack */
+    void clear() {
+        stackTop = nullptr;
+        size = 0;
+    }
+
+ private:
+    std::shared_ptr<Node<value_type>> stackTop =
+        {};                /**< Pointer to the stack */
+    std::size_t size = 0;  ///< size of stack
+};
+
+#endif  // DATA_STRUCTURES_STACK_HPP_