【面试题59 - II. 队列的最大值】（普通队列）

 【解题思路】

        刚开始用了优先队列PriorityQueue，在一组测试样例中过不了，输出总是[], [], [], [], [], [], [], 16, [], 22，正确答案应该是[], [], [], [], [], [], [], 96, [], 16。经过调试，终于想起了，这是优先队列，默认将队列按照升序排列，而此题应该使用普通队列。

 

class MaxQueue {
    int max = -99999;
    Queue queue;
    public MaxQueue() {
        queue = new LinkedList();
    }
    
    public int max_value() {
        if(queue.isEmpty())
        {
            return -1;
        }
        return max;
    }
    
    public void push_back(int value) {
        if(value > max)
        {
            max = value;
        }
        queue.offer(value);
    }
    
    public int pop_front() {
        if(queue.isEmpty())
        {
            return -1;
        }
        int num = queue.poll();
        if(num == max)
        {
            max = -99999;
            Queue q = new LinkedList();
            while(!queue.isEmpty())
            {
                int tmp = queue.peek();
                if(tmp > max) max = tmp;
                q.offer(queue.poll());
            }
            while(!q.isEmpty())
            {
                queue.offer(q.poll());
            }
        }
        return num;
    }
}

/**
 * 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();
 */