https://programmers.co.kr/learn/courses/30/lessons/12985
import Foundation
func solution(_ n:Int, _ a:Int, _ b:Int) -> Int {
var answer = 0
var aValue = a
var bValue = b
while aValue != bValue {
if aValue % 2 == 1 {
aValue = aValue / 2 + 1
} else {
aValue = aValue / 2
}
if bValue % 2 == 1 {
bValue = bValue / 2 + 1
} else {
bValue = bValue / 2
}
answer += 1
}
return answer
}