171. Excel Sheet Column Number

Description

Related to question

Excel Sheet Column Title

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

Solution

Iterative

从前向后遍历，做进制转换。

class Solution {
    public int titleToNumber(String s) {
        int num = 0;
        
        for (int i = 0; i < s.length(); ++i) {
            num = num * 26 + (s.charAt(i) - 'A' + 1);
        }
        
        return num;
    }
}