题目描述
示例1
示例2
做题思路
代码
class MaxQueue {
Queue<Integer> queue;//普通队列
Deque<Integer> deque;//递减双端队列
public MaxQueue() {
queue = new LinkedList<>();//队列初始化
deque = new LinkedList<>();//双端队列初始化
}
public int max_value() {
return deque.isEmpty() ? -1 : deque.peekFirst();//若队列为空返回-1,否则返回deque左顶端元素
}
public void push_back(int value) {
queue.offer(value);//元素入队
while(!deque.isEmpty() && deque.peekLast() < value)
deque.pollLast();//如果deque非空且右顶端元素小于value则出队
deque.offerLast(value);//value入deque右端,保持deque递减
}
public int pop_front() {
if(queue.isEmpty()) return -1;
if(queue.peek().equals(deque.peekFirst()))
deque.pollFirst();//如果deque左顶端元素等于queue出队元素,则弹出deque左顶端元素
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();
*/