class CircularQueue {
   constructor(size) {

     this.queue = [];
     this.read = 0;
     this.write = 0;
     this.max = size - 1;

     while (size > 0) {
        this.queue.push(null);
        size--;
     }

   }

   print() {
     return this.queue;
   }


   enqueue(item) {
    // Only change code below this line
    if(this.write > this.max){
        this.write = this.write - this.max - 1;
    }
    
    if(this.queue[this.write] !== null){
        return null;    
    }
    
    this.queue[this.write] = item;
    this.write = this.write + 1;
    return item;
    // Only change code above this line
   }

   dequeue() {
    // Only change code below this line
    
    if(this.read > this.max){
        this.read = this.read - this.max - 1;
    }
    
    if(this.queue[this.read] === null){
        return null;
    }
    
    
    
    var readinfo = this.queue[this.read];
    this.queue[this.read] = null;
    this.read = this.read + 1;
    
    return readinfo;
    
    // Only change code above this line
   }
}