192. Excel Sheet Column Number

Easy · Math

Given a string representing a column title as it appears in an Excel sheet, return the corresponding column number.

In Excel, columns are labeled as follows: A=1, B=2, ..., Z=26, AA=27, AB=28, ..., AZ=52, BA=53, and so on. This is essentially a base-26 number system where A-Z represent digits 1-26 (not 0-25).

Examples

Example 1
Input: "A"
Output: 1
Explanation: A is the first column, so the answer is 1.
Example 2
Input: "AB"
Output: 28
Explanation: A=1, B=2, so AB = 1*26 + 2 = 28.
Example 3
Input: "ZZ"
Output: 702
Explanation: Z=26, so ZZ = 26*26 + 26 = 676 + 26 = 702.

Constraints