171. Excel Sheet Column Number

Problem

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

Solution

class Solution {
public:
    int titleToNumber(string s) {
            int len = s.length();
    int sum = 0;
    for(int i=len-1,j=0;i>=0;i--,j++){
        sum += (int(s[i])-64)*pow(26,j);
    }
    return sum;
    }
};

Result