LeetCode面试题59.队列的最大值

存储最大值的用双向队列，从后面压入，从前面弹出

class MaxQueue {
    Queue<Integer> queue;
    LinkedList<Integer> maxqueue;
    
    public MaxQueue() {
        queue = new LinkedList<>();
        maxqueue = new LinkedList<>();
    }
    
    public int max_value() {
        if(maxqueue.isEmpty()) return -1;
        return maxqueue.peekFirst();
    }
    
    public void push_back(int value) {
        queue.add(value);
        while(!maxqueue.isEmpty() && value > maxqueue.getLast()){
            maxqueue.removeLast();
        }
        maxqueue.add(value);
    }
    
    public int pop_front() {
        if(queue.isEmpty()) return -1;
        if(maxqueue.peek().equals(queue.peek())){
            maxqueue.poll();
        }
        return queue.poll();
    }
}

/**
 * Your MaxQueue object will be instantiated and called as such:
 * MaxQueue obj = new MaxQueue();
 * int param_1 = obj.max_value();
 * obj.push_back(value);
 * int param_3 = obj.pop_front();
 */