171. Excel Sheet Column Number--LeetCode Record

Related to question Excel Sheet Column Title

Given a column title as appear in an Excel sheet, return its corresponding column number.

For example:

A -> 1B -> 2C -> 3...Z -> 26AA -> 27AB -> 28 

class Solution {    func titleToNumber(s: String) -> Int {        var sum:Int = 0        var basic:Int = 1        for (index, ch) in String(s).unicodeScalars.enumerate().reverse() {            let chInt = Int(ch.value) - 64            sum += basic * chInt            basic *= 26        }        return sum    }}

TestCase

"A""AB""BA""ABC""CAB"