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
题意：给定Excel工作表中显示的列标题，返回其对应的列号；
解法：列标题应当是用字母表示的27进制，每当超过27时便进一（A-1; B-2; C-3…Z-26）；例如对于AZ来说，对其再加一为BA；
Java
class Solution {
public int titleToNumber(String s) {
int columnNumber = 0;
int order = 1;
for (int i = s.length() - 1; i >= 0; i--) {
columnNumber += (s.charAt(i) - 'A' + 1) * order;
order *= 26;
}
return columnNumber;
}
}
