171. Excel Sheet Column Number

• Difficulty: Easy

• Topics: Math

• Similar Questions:

  • Excel Sheet Column Title

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

Solutions:

class Solution {
public:
    int titleToNumber(string s) {
        int ret = 0;
        for (int i = 0; i < s.length(); ++i) {
            ret = 26 * ret + (s[i] - 'A' + 1); // be careful about overflow
        }

        return ret;
    }
};