171. Excel Sheet Column Number

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

难度：easy
题目：给定Excel 表单里的一列名，返回其整数表示。
思路：26进制
Runtime: 1 ms, faster than 100.00% of Java online submissions for Excel Sheet Column Number.Memory Usage: 34.5 MB, less than 86.88% of Java online submissions for Excel Sheet Column Number.
class Solution {
public int titleToNumber(String s) {
int result = 0, scale = 1;
for (int i = s.length() – 1; i >= 0; i–) {
result += (s.charAt(i) – ‘A’ + 1) * scale;
scale *= 26;
}

return result;
}
}