LeetCode: Excel Sheet Column Number

Problem:

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 

Credits: Special thanks to @ts for adding this problem and creating all test cases.

Solution:

class Solution {
public:
    int titleToNumber(string s) {
        
        int len=s.length();
        if(len==0) return 0;
        
        int sum=0;
        for(int i=0;i<len;i++)
        {
            int num=s[i]-'A'+1;
            sum+=num*pow(26,len-1-i);
        }
        return sum;
    }
};