class SequentialQueue{	//if you want it to go backwards, too bad
	next(){
		return this.i++;
	}
	constructor(start = 0){
		this.i = start;
	}
}
const que = new SequentialQueue(0);
for(let i = 0; i < 10; i++){
	console.log(que.next());
}

const kNearestNeighbors = (data, labels, point, k = 3) => {
  const kNearest = data
    .map((el, i) => ({
      dist: Math.hypot(...Object.keys(el).map(key => point[key] - el[key])),
      label: labels[i]
    }))
    .sort((a, b) => a.dist - b.dist)
    .slice(0, k);

  return kNearest.reduce(
    (acc, { label }, i) => {
      acc.classCounts[label] =
        Object.keys(acc.classCounts).indexOf(label) !== -1
          ? acc.classCounts[label] + 1
          : 1;
      if (acc.classCounts[label] > acc.topClassCount) {
        acc.topClassCount = acc.classCounts[label];
        acc.topClass = label;
      }
      return acc;
    },
    {
      classCounts: {},
      topClass: kNearest[0].label,
      topClassCount: 0
    }
  ).topClass;
};
const data = [[0, 0], [0, 1], [1, 3], [2, 0]];
const labels = [0, 1, 1, 0];

kNearestNeighbors(data, labels, [1, 2], 2); // 1
kNearestNeighbors(data, labels, [1, 0], 2); // 0

const binomialCoefficient = (n, k) => {
  if (Number.isNaN(n) || Number.isNaN(k)) return NaN;
  if (k < 0 || k > n) return 0;
  if (k === 0 || k === n) return 1;
  if (k === 1 || k === n - 1) return n;
  if (n - k < k) k = n - k;
  let res = n;
  for (let j = 2; j <= k; j++) res *= (n - j + 1) / j;
  return Math.round(res);
};

binomialCoefficient(8, 2); // 28

const arithmeticProgression  = (n, lim) =>
  Array.from({ length: Math.ceil(lim / n) }, (_, i) => (i + 1) * n );
  
arithmeticProgression(5, 25); // [5, 10, 15, 20, 25]

const head = arr => (arr && arr.length ? arr[0] : undefined);

head([1, 2, 3]); // 1
head([]); // undefined
head(null); // undefined
head(undefined); // undefined

//JavaScript program to swap two variables

//take input from the users
let a = prompt('Enter the first variable: ');
let b = prompt('Enter the second variable: ');

// XOR operator
a = a ^ b
b = a ^ b
a = a ^ b

console.log(`The value of a after swapping: ${a}`);
console.log(`The value of b after swapping: ${b}`);