LeetCode - Excel Sheet Column Number

Excel Sheet Column Number

2015.1.23 17:54

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:

　　This is a reversed version of the paired question. So do it backward.

Accepted code:

// 1AC, nice and easy
class Solution {
public:
    int titleToNumber(string s) {
        int base = 1;
        int i;
        int len = s.length();
        int sum = 0;
        
        for (i = 0; i < len; ++i) {
            sum = sum * 26 + (s[i] - 'A');
        }
        for (i = 1; i < len; ++i) {
            base *= 26;
            sum += base;
        }
        sum += 1;
        
        return sum;
    }
};