Topic description
Define a queue and implement the function max_value to get the maximum value in the queue, requiring the function MAX_VALUE, PUSH_BACK, and POP_FRONT's average time complexity to be O (1).
If the team is empty, POP_FRONT and MAX_VALUE need to return -1
Method 1: Violence

class MaxQueue {
    int[] q = new int[20000];
    int begin = 0;
    int end = 0;

    public MaxQueue() {
        
    }
    
    public int max_value() {
        int ans = -1;
        for(int i = begin;i!=end;i++){
            if(q[i]>ans){
                ans = q[i];
            }
        }
        return ans;
    }
    
    public void push_back(int value) {
        q[end++] = value;
    }
    
    public int pop_front() {
        if(begin == end){
            return -1;
        }
        return q[begin++];

    }
}

Method Two:
Use oneDouble-end queue DequeWhen you enter the team, if DequeTailelementBe less thanThe element value of the team will be entered.Elements smaller than value all out of the teamAfterwards, enter the team; otherwise it will enter the team directly.

class MaxQueue {
    Queue<Integer> q;
    Deque<Integer> d; 

    public MaxQueue() {
        q = new LinkedList<Integer>();
        d = new LinkedList<Integer>();
    }
    
    public int max_value() {
        if(d.isEmpty()){
            return -1;
        }
        return d.peekFirst();// Get the first element of the double-end queue
    }
    
    public void push_back(int value) {
        while(!d.isEmpty()&& d.peekLast()<value){
            d.pollLast();// Get and remove the last element of the double-end queue
        }
        d.offerLast(value);/ / Insert the specified element into the end of the double-end queue
        q.offer(value);/ / Add the specified element to the end of this queue
    }
   
    public int pop_front() {
        if(q.isEmpty()){
            return -1;
        }
        int ans = q.poll();/ / Get the element of the team head and delete the element
        if(ans == d.peekFirst()){
            d.pollFirst();// Get and remove the first element of the double-end queue
        }
        return ans;
    }
}

/**
 * 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();
 */