Data Structures: Create a Circular Queue

Data Structures: Create a Circular Queue
0

#1

Tell us what’s happening:
Hey all,

Struggling with this one. I’m failing the last test: " Trying to dequeue past the write pointer returns null and does not advance the write pointer." Any help would be appreciated.

Your code so far


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;
   }

   isFull(){
     let count = 0;

     for (let i = 0; i < this.queue.length; i++){
       if (this.queue[i] == null){
        count++
       }
     }

     if (count > 0){
       return false;
     } 
     return true;
   }

   enqueue(item) {
    // Only change code below this line
    if (this.isFull()) {
         this.write = 0;
         }
         if (this.queue[this.write] === null){
           this.queue[this.write] = item;
           this.write++;
           return this.queue[this.write - 1];
         } else {
           return null;
         }
    // Only change code above this line
   }

   dequeue() {
    // Only change code below this line
    if (this.read > this.max){
      this.read = 0;
    }
      if (this.read <= this.write){
          var result = this.queue.splice(this.read, 1, null);
          if (this.read < this.write){
           this.read++; 
          }
          return result[0];
        } else {
          return null;
        }
      }
    // Only change code above this line
   }

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:62.0) Gecko/20100101 Firefox/62.0.

Link to the challenge:
https://learn.freecodecamp.org/coding-interview-prep/data-structures/create-a-circular-queue


#2

Got it to work!

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;
   }

   isFull(){
     let count = 0;

     for (let i = 0; i < this.queue.length; i++){
       if (this.queue[i] == null){
        count++
       }
     }

     if (count > 0){
       return false;
     } 
     return true;
   }

   enqueue(item) {
    // Only change code below this line
    if (this.isFull()) {
         this.write = 0;
         }
     if (this.write > this.max){
       this.write = 0;
     }
         if (this.queue[this.write] == null){
           this.queue[this.write] = item;
           this.write++;
           return this.queue[this.write - 1];
         } else {
           return null;
         }
    // Only change code above this line
   }

   dequeue() {
    // Only change code below this line
    console.log(this.queue);
    if (this.read > this.max){
      this.read = 0;
    }
      if (this.queue[this.read] !== null){
          var result = this.queue.splice(this.read, 1, null);
          if (this.queue[this.read + 1] !== null){
           this.read++; 
          return result[0];
          } else {
            return result[0];
          }
        } else {
          return null;
        }
      }
    // Only change code above this line
   }