1472.cpp

class BrowserHistory {
    struct Node {
        Node *next, *prev;
        string val;
        Node(string val = "#", Node *prev = nullptr, Node *next = nullptr)
            : val(val), prev(prev), next(next) {}
    };
    Node *head = nullptr, *tail = nullptr, *crnt = nullptr;

  public:
    BrowserHistory(string homepage) { crnt = head = tail = new Node(homepage); }

    void visit(string url) {
        for (Node *t = tail->next; t;) {
            Node *tmp = t;
            t = t->next;
            delete tmp;
        }
        crnt = tail = tail->next = new Node(url, tail, nullptr);
    }

    string back(int steps) {
        while (steps-- && crnt->prev)
            tail = crnt = crnt->prev;
        return crnt->val;
    }

    string forward(int steps) {
        while (steps-- && crnt->next)
            tail = crnt = crnt->next;
        return crnt->val;
    }
};