Leetcode - 1670 design front, middle and rear queues (Design - two double ended queues)

Two double ended queues

class FrontMiddleBackQueue {
    
    // Divide all values into two parts 
    // The first half is placed in deque1 
    private Deque<Integer> deque1;
    // The second half is placed in deque2
    private Deque<Integer> deque2;
    // send deque1 The number of values of is not equal to deque2 The number of values of is equal ( The number of values is even )  Not compare deque2 More than a ( The number of values is odd )
    public FrontMiddleBackQueue() {
    
        deque1 = new LinkedList<>();
        deque2 = new LinkedList<>();
    }
    public void makeBalance(){
    
        // send deque1 The number of values of is not equal to deque2 The number of values of is equal ( The number of values is even )  Not compare deque2 More than a ( The number of values is odd )
        // There are only two kinds of dissatisfaction 
        //deque1 The number ratio of values deque2 The number of values is two more 
        if(deque1.size() > deque2.size()+1)
           deque2.offerFirst(deque1.pollLast());
           //deque2 The number ratio of values deque1 The number of values is one more 
        if(deque2.size() > deque1.size())
          deque1.offerLast(deque2.pollFirst());
    }
    public void pushFront(int val) {
    
        // Put it in deque1 In front of 
        deque1.offerFirst(val);
        // Maintain a balance 
        makeBalance();
    }
    
    public void pushMiddle(int val) {
    
        // If the existing value is 1 3 2
        // after makeBalance deque1 1 3 deque2 2
        // here pushMiddle 4
        // But when the value is an odd number  pushMiddle It's on the  3  Previous   So we need to 3  Put in deque2  And then  4  Put in deque1
        // deque1 1 4 deque2 3 2 
       if(deque1.size() > deque2.size())
           deque2.offerFirst(deque1.pollLast());
        // If the existing value is 1 4 3 2 
        // be deque1 1 4 deque2 3 2
        //pushMiddle 5
        // Put... Directly 5 Put in deque1
        //deque1 1 4 5 deque2 3 2
       deque1.offerLast(val);
    }
    
    public void pushBack(int val) {
    
        // Put it directly in deque2  end 
        deque2.offerLast(val);
        // Keep the balance 
        makeBalance();
    }
    
    public int popFront() {
    
        // stay deque1 Not empty   Go straight back to deque1 Head end value 
        if(deque1.size() != 0){
    
           int val =  deque1.pollFirst();
           makeBalance();
           return val;
        }
        // because deque1 The number of values of must be greater than deque2 It's worth a lot   If deque1 If it is empty, the current number of values is 0
        else
           return -1;
    }
    
    public int popMiddle() {
    
        // The current value is an odd number 
        //1 3 5 7 9
        // deque1 1 3 5 deque2 7 9
        // When the value is even 
        // 1 3 5 7
        // deque1 1 3 deque2 5 7
        // Anyway  middle  All are deque1 End value of 
        if(deque1.size() != 0){
    
            int val = deque1.pollLast();
            makeBalance();
             return val;
        }
        else
          return -1;
    }
    
    public int popBack() {
    
        // When the number of values is 0 when  deque1  and deque2  It's all empty time   return -1
       if(deque1.size() == 0 && deque2.size() == 0){
    
           return -1;
       }
       else if(deque2.size() != 0){
     // When the number of values is greater than or equal to 2 when  deque2 There must be value in   return  deque2 End value 
           int val = deque2.pollLast();
           makeBalance();
           return val;
       }else{
    //  When the number of values is 1  when  deque1.size() == 1 deque2.size() == 0  return deque1 End value of 
            int val = deque1.pollLast();
           makeBalance();
           return val;
       }
       
    }
}

/** * Your FrontMiddleBackQueue object will be instantiated and called as such: * FrontMiddleBackQueue obj = new FrontMiddleBackQueue(); * obj.pushFront(val); * obj.pushMiddle(val); * obj.pushBack(val); * int param_4 = obj.popFront(); * int param_5 = obj.popMiddle(); * int param_6 = obj.popBack(); */