A01 Implement Queue with Limited Size of Arrays, Node.js

A01 Implement Queue with Limited Size of Arrays

/* 
A01 Implement Queue with Limited Size of Arrays
解法： 用2-D array
*/
var Queue = function(arraySize){
  this.arraySize = arraySize;
  this.q = [[]]
  this.used = 0 ;
}

Queue.prototype.push = function(num){
  let len = this.q.length;
  let arr = this.q[len-1]
  arr.push(num);
  this.used++;
  if(arr.length == this.arraySize){
    this.q.push([]);
  }
}

Queue.prototype.shift =function(){
  if(this.used > 0){
    this.used--;
    let res = this.q[0].shift();
    if(this.q[0].length == 0 && this.used >0) {
      this.q.shift(); // get rid of the empty []
    }
    return res; 
  }
  else{
    return null;
  }
}

Queue.prototype.getFront = function(){
  if(this.used > 0)
    return this.q[0][0];
  else return null; 
}

// 
let q = new Queue(3)
console.log(q)
q.push(1); q.push(2); q.push(3)
console.log(q)
q.push(4); q.push(5);
console.log(q)

let x = q.shift() 
console.log("x=", x)
console.log(q)
console.log("front = ", q.getFront());

q.shift()
q.shift()
console.log(q)
q.shift()
console.log(q) 
q.shift()
q.shift()
q.shift()
console.log(q )


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