剑指 Offer 59 - II. 队列的最大值

package leetcode;

import java.util.LinkedList;
import java.util.Queue;

public class offer_59_2 {
    Queue<Integer> que1;
    LinkedList<Integer> que2;
    public offer_59_2() {
        que1=new LinkedList<Integer>();
        que2=new LinkedList<Integer>();
    }
    
    //双向链表中的头结点是最大值
    public int max_value() {
        if(que2.isEmpty()) {
            return -1;
        }
        return que2.peek();
        
    }
    
    public void push_back(int value) {
        que1.add(value);
        //维持一个递减序列
        while(!que2.isEmpty()&&que2.peekLast()<=value) {
            que2.pollLast();
        }
        que2.add(value);
    }
    
    public int pop_front() {
        if(que1.isEmpty()) {
            return -1;
        }
        int temp=que1.poll();
        if(!que2.isEmpty()&&temp==que2.peek()) {
            que2.poll();
        }
        return temp;
    }
}