# 171_Excel_Sheet_Column_Number
###### tags: `leetcode`
## Problem Statement
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

- Constraints:

> 1 <= s.length <= 7
s consists only of uppercase English letters.
s is between "A" and "FXSHRXW".

## Solution
- Reverse the string to add in the correct order.

reverse(begin(s), end(s));

- Just let every element has 26 carry and add the number one by one.

for (auto &i: s)
{
    ans+= cnt* (i- 'A'+ 1);
    cnt*= 26;
}