UniqueQueue.h

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/*
 * SyntaxTutor - Interactive Tutorial About Syntax Analyzers
 * Copyright (C) 2025 Jose R. (jose-rzm)
 *
 * This program is free software: you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */
 
#ifndef UNIQUEQUEUE_H
#define UNIQUEQUEUE_H
#include <queue>
#include <unordered_set>

template <typename T> class UniqueQueue {
  public:
    void push(const T& value) {
        if (seen_.insert(value).second) {
            queue_.push(value);
        }
    }

    void pop() {
        if (!queue_.empty()) {
            queue_.pop();
        }
    }

    const T& front() const { return queue_.front(); }

    bool empty() const { return queue_.empty(); }

    void clear() {
        while (!queue_.empty())
            queue_.pop();
        seen_.clear();
    }
 
  private:
    std::queue<T>         queue_; 
    std::unordered_set<T> seen_;  
};
#endif // UNIQUEQUEUE_H