LeetCode高频面试60天打卡日记Day07

Day07

idea:

1、初始化一个队列存放每次push_back的数据

2、初始化一个双端队列，要求该队列front–>back为递减，保证front始终为最大值

class MaxQueue {
    
    
    private Queue<Integer> queue = new LinkedList<>();
    private Deque<Integer> deque = new ArrayDeque<>();
    public MaxQueue() {
    
    
       
    }
    
    public int max_value() {
    
    
       return deque.isEmpty() ? -1:deque.peekFirst();
    }
    
    public void push_back(int value) {
    
    
        queue.offer(value);
        //deque成为递减队列
        while(!deque.isEmpty()&&deque.peekLast()<value){
    
    
            deque.pollLast();
        }
        deque.offerLast(value);
    }
    
    public int pop_front() {
    
    
        Integer result = queue.poll();  //queue存放入队列的各个数据
        if(!deque.isEmpty()&&deque.peekFirst().equals(result)){
    
    
            deque.pollFirst();
        }
        return result==null ? -1:result;
    }
}

/**
 * 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();
 */