171. Excel Sheet Column Number

Description

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

For example:

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

Example 1:

Input: "A"
Output: 1
Example 2:

Input: "AB"
Output: 28
Example 3:

Input: "ZY"
Output: 701

Answer

package main

import (
    "fmt"
    "math"
)

func titleToNumber(s string) int {

    var result int
    count := 0
    for i := len(s) - 1; i >= 0; i-- {

        result += int(s[i]-'A'+1) * int(math.Pow(float64(26), float64(count)))
        count++
    }

    return result

}
func main() {
    fmt.Println(titleToNumber("A"))
    fmt.Println(titleToNumber("B"))
    fmt.Println(titleToNumber("AB"))
    fmt.Println(titleToNumber("ZY"))
}