combination-generator

const combinationUtil = (arr, length, k, index, result, i) => {
  if (index === k) {
    let str = ''

    for (let j = 0; j < k; j++) {
      str += result[j] + ' '
    }

    console.log(str)

    return
  }

  if (i >= length) {
    return
  }

  result[index] = arr[i]
  combinationUtil(arr, length, k, index + 1, result, i + 1)
  combinationUtil(arr, length, k, index, result, i + 1)
}

const solve = ([n, k]) => {
  const arr = [...Array(n).keys()].map(x => ++x)
  const length = arr.length

  let result = []

  combinationUtil(arr, length, k, 0, result, 0)
}

solve([5, 2])