Excel Sheet Column Number

Desicription

Given a column title as appear in an Excel sheet, return its corresponding column number.

For example:

1
2
3
4
5
6
7
8
A -> 1
B -> 2
C -> 3
...
Z -> 26
AA -> 27
AB -> 28 
...

Example 1:

1
2
Input: "A"
Output: 1

Example 2:

1
2
Input: "AB"
Output: 28

Example 3:

1
2
Input: "ZY"
Output: 701

Solution

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5
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9
class Solution {
public:
    int titleToNumber(string s) {
        int res = 0;
        for(int i = s.size() - 1; i >= 0; i--)
            res += pow(26, s.size() - 1 - i) * (s[i] - 'A' + 1);
        return res;
    }
};