59 - ||队列的最大值
面试题59 - II. 队列的最大值
难度中等92
请定义一个队列并实现函数 max_value 得到队列里的最大值,要求函数max_value、push_back 和 pop_front
的均摊时间复杂度都是O(1)。若队列为空,pop_front 和 max_value 需要返回 -1
示例 1:
输入: ["MaxQueue","push_back","push_back","max_value","pop_front","max_value"] [[],[1],[2],[],[],[]] 输出: [null,null,null,2,1,2]
示例 2:
输入: ["MaxQueue","pop_front","max_value"] [[],[],[]] 输出: [null,-1,-1]
双端队列
Deque<Integer> que;
Deque<Integer> deq;
public MaxQueue() {
que = new LinkedList<>();//add and dele
deq = new LinkedList<>();//find max value
}
public int max_value() {
return que.size()>0 ? deq.peek() : -1;
}
public void push_back(int value) {
que.offer(value);
while(deq.size()>0 && deq.peekLast()<value){
deq.pollLast();
}
deq.offer(value);
}
public int pop_front() {
int tmp = que.size()>0? que.poll() : -1;
//deq size > 0 and tmp 包含 maxValue 返回 deq的最大值
if(deq.size()>0 && tmp == deq.peek()){
deq.poll();
}
return tmp;
}