Rearranging cards into groups in JavaScript

Problem

We are required to write a JavaScript function that takes in an array of numbers, arr, as the first argument and a number, num, as the second argument.

The numbers in the array are in the range [1, 13], limits inclusive, representing the 1-based index of playing cards.

Our function should determine whether there exists a way to rearrange the cards into groups so that each group is size num, and consists of num consecutive cards.

For example, if the input to the function is

Input

const arr = [1, 4, 3, 2];
const num = 2;

Output

const output = 2;

Output Explanation

Because the cards can be rearranged as [1, 2], [3, 4]

Example

Following is the code −

 Live Demo

const arr = [1, 4, 3, 2];
const num = 2;
const canRearrange = (arr = [], num = 1) => {
   const find = (map, n, num) => {
   let j = 0
   while(j < num) {
      if(!map[n + j]) return false
         else map[n + j] -= 1
         j++
      }
      return true
   }
   let map = {}
   arr.sort(function(a, b) {return a - b})
   for(let n of arr) {
      map[n] = map[n] ? map[n] + 1 : 1
   }
   for(let n of arr) {
      if(map[n] === 0 || find(map, n, num)) continue
         else return false
   }
   return true
};
console.log(canRearrange(arr, num));

Output

true