How many groups (more than 1 number per group) of an integer list can be split out, each sorted, and concatenated together to produce the same result as sorting the list?

splittable-sort-array.js

function solution(A) {
  let index = 0
  let results = 0
  let remainder = 0
  let number
  while (index < A.length) {
    number = A[index]
    for (let i = index + 1; i < A.length; i++) {
      if (number > A[i]) {
        index = i
      }
    }
    
    if (number !== A[index]) {
      results += 1
      remainder = false
    }
    else remainder = true
    
    index += 1
  }
 
  if (remainder) results += 1
  return results > 1 ? results : 0
}

console.log(solution([1,2,3,4,5])) // 0 => no subgroups, just sort it
console.log(solution([5,4,3,2,1])) // 0 => no subgroups, just sort it
console.log(solution([2,1,3,4,5])) // 2 => [2,1],[3,4,5]
console.log(solution([2,1,4,3,6,5])) // 3 => [2,1],[4,3],[6,5]
console.log(solution([2,1,5,6,3])) // 2 => [2,1],[5,6,3]