Given a column title as appears in an Excel sheet, return its corresponding column number.
Example:
A -> 1
B -> 2
C -> 3
...
Z -> 26
AA -> 27
AB -> 28
Solution:
Time: O(n) Space: O(1)
public class Solution { public int titleToNumber(String A) { int size = 26; int n = A.length() - 1; int number = 0; for (int i = n; i >= 0; i --) { char c = A.charAt(i); number += (c - 'A' + 1) * (int) Math.pow(size, n - i); } return number; } }