doubly_linked_list.h

#ifndef DOUBLY_LINKED_LIST_H
#define DOUBLY_LINKED_LIST_H
 
#ifdef ENABLE_LINKED_LIST_VISUALIZATION
#include "../../visualization/list_visual/linked_list_visualization.h"
#endif
 
#ifdef __cplusplus
#include <iostream>
#include <memory>
#include <string>
#include <type_traits>
#include <vector>
#endif

template <typename T> class doubly_linked_list {
  public:
    inline explicit doubly_linked_list(std::vector<T> _elements = {}) noexcept
        : root(nullptr), tail(nullptr) {
        if (!_elements.empty()) {
            for (T& x : _elements) {
                this->push_back(x);
            }
        }
    }

    inline explicit doubly_linked_list(const doubly_linked_list& l)
        : root(l.root), tail(l.tail), _size(l._size) {}

    inline doubly_linked_list& operator=(const doubly_linked_list& l) {
        root = l.root;
        tail = l.tail;
        _size = l._size;
        return *this;
    }

    inline bool empty() { return root == nullptr; }

    inline size_t size() { return _size; }
 
    class Iterator;

    inline Iterator begin() { return Iterator(root); }

    inline Iterator end() { return Iterator(nullptr); }

    inline bool search(T key);

    inline void push_back(T key);

    inline void push_front(T key);

    inline void erase(T key);

    inline std::vector<T> elements();

    inline void reverse();

    inline void visualize();

    inline friend std::ostream& operator<<(std::ostream& out, doubly_linked_list<T>& l) {
        out << '{';
        std::shared_ptr<node> head = l.root;
        while (head) {
            out << head->val << ' ';
            head = head->next;
        }
        out << '}' << '\n';
        return out;
    }
 
  private:
    struct node {
        T val;
        std::shared_ptr<node> next;
        std::shared_ptr<node> prev;
        node(T key = 0) : val(key), next(nullptr), prev(nullptr) {}
    };
    std::shared_ptr<node> root;
    std::shared_ptr<node> tail;
    size_t _size{0};
 
    std::string generate();
};
 
template <typename T> bool doubly_linked_list<T>::search(T key) {
    if (this->empty()) {
        return false;
    } else {
        std::shared_ptr<node> t = root;
        while (t != nullptr && t->val != key) {
            t = t->next;
        }
        return (t == nullptr || t->val != key) ? false : true;
    }
    return false;
}
 
template <typename T> void doubly_linked_list<T>::push_back(T key) {
    std::shared_ptr<node> p = std::make_shared<node>(key);
    p->prev = tail;
    p->next = nullptr;
    if (tail != nullptr) {
        tail->next = p;
    }
    if (root == nullptr) {
        root = p;
    }
    tail = p;
    _size++;
}
 
template <typename T> void doubly_linked_list<T>::push_front(T key) {
    std::shared_ptr<node> p = std::make_shared<node>(key);
    p->next = root;
    p->prev = nullptr;
    if (root != nullptr) {
        root->prev = p;
    }
    if (tail == nullptr) {
        tail = p;
    }
    root = p;
    _size++;
}
 
template <typename T> void doubly_linked_list<T>::erase(T key) {
    if (root == nullptr) {
        return;
    }
    std::shared_ptr<node> head = root;
    while (head && head->val != key) {
        head = head->next;
    }
    if (head == nullptr) {
        return;
    }
    if (head->next != nullptr) {
        if (head == root) {
            root = root->next;
        }
        head->next->prev = head->prev;
    }
    if (head->prev != nullptr) {
        if (head == tail) {
            tail = tail->prev;
        }
        head->prev->next = head->next;
    }
}
 
template <typename T> std::vector<T> doubly_linked_list<T>::elements() {
    std::vector<T> _elements;
    if (this->empty()) {
        return _elements;
    }
    std::shared_ptr<node> head = root;
    while (head) {
        _elements.push_back(head->val);
        head = head->next;
    }
    return _elements;
}
 
template <typename T> void doubly_linked_list<T>::reverse() {
    std::shared_ptr<node> current = root;
    std::shared_ptr<node> temp{nullptr};
 
    while (current != nullptr) {
        temp = current->prev;
        current->prev = current->next;
        current->next = temp;
        current = current->prev;
    }
 
    if (temp) {
        root = temp->prev;
    }
}
 
template <typename T> std::string doubly_linked_list<T>::generate() {
    std::string gen;
    gen += "rankdir=LR;";
    gen += '\n';
    gen += "node [shape=record;]";
    gen += '\n';
    std::vector<T> els = this->elements();
    if (std::is_same_v<T, std::string> || std::is_same_v<T, char>) {
        for (auto& x : els) {
            gen += x;
            gen += " [label=<{ ";
            gen += x;
            gen += " | }>] ;";
            gen += '\n';
        }
 
        std::shared_ptr<node> curr = root;
        while (curr->next) {
            gen += curr->val;
            gen += ":ref -> ";
            gen += curr->next->val;
            gen += ":data [arrowhead=vee, arrowtail=dot, dir=both];";
            gen += '\n';
 
            gen += curr->next->val;
            gen += ":data -> ";
            gen += curr->val;
            gen += ":ref [arrowhead=vee, arrowtail=dot, dir=both];";
            gen += '\n';
 
            curr = curr->next;
        }
    } else {
        for (auto& x : els) {
            gen += std::to_string(x);
            gen += " [label=<{ ";
            gen += std::to_string(x);
            gen += " | }>] ;";
            gen += '\n';
        }
 
        std::shared_ptr<node> curr = root;
        while (curr->next) {
            gen += std::to_string(curr->val);
            gen += ":ref -> ";
            gen += std::to_string(curr->next->val);
            gen += ":data [arrowhead=vee, arrowtail=dot, dir=both];";
            gen += '\n';
 
            gen += std::to_string(curr->next->val);
            gen += ":data -> ";
            gen += std::to_string(curr->val);
            gen += ":ref [arrowhead=vee, arrowtail=dot, dir=both];";
            gen += '\n';
 
            curr = curr->next;
        }
    }
    return gen;
}
 
#ifdef LINKED_LIST_VISUALIZATION_H
template <typename T> void doubly_linked_list<T>::visualize() {
    std::string generated = this->generate();
    linked_list_visualization::visualize(generated);
}
#endif

template <typename T> class doubly_linked_list<T>::Iterator {
  private:
    std::shared_ptr<node> curr_root;
 
  public:
    explicit Iterator(const std::shared_ptr<node>& l) noexcept : curr_root(l) {}

    Iterator& operator=(std::shared_ptr<node> current) {
        this->curr_root = current;
        return *(this);
    }

    Iterator& operator++() {
        if (curr_root) {
            curr_root = curr_root->next;
        }
        return *(this);
    }

    Iterator operator++(int) {
        Iterator it = *this;
        ++*(this);
        return it;
    }

    Iterator& operator--() {
        if (curr_root) {
            curr_root = curr_root->prev;
        }
        return *(this);
    }

    Iterator operator--(int) {
        Iterator it = *this;
        --*(this);
        return it;
    }

    bool operator!=(const Iterator& it) { return curr_root != it.curr_root; }

    T operator*() { return curr_root->val; }
};
 
#endif