Excel Sheet Column Number

https://leetcode.com/problems/excel-sheet-column-number/description/

Related to questionExcel Sheet Column Title

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

Thoughts

26进制转换. 只是每次要多加1因为它要的不是0~25而是1~26.

Code

class Solution {
    public int titleToNumber(String s) {
        int sum = 0;
        for (int i = s.length() - 1; i >= 0; i--) {
            char c = s.charAt(i);
            sum += Math.pow(26, s.length() - 1 - i) * (c - 'A' + 1);
        }

        return sum;
    }
}

Analysis

时间复杂度O(N), N为字符串长度. 空间O(1).