# [171. Excel Sheet Column Number](https://leetcode.com/problems/excel-sheet-column-number/description/) # 思路 第[168题](https://leetcode.com/problems/excel-sheet-column-title/description/)是将10进制转换为26进制,这题是将26进制转换为10进制. 例:将k进制数"abcd"转换为10进制数:`res = d * k^0 + c * k^1 + b * k^2 + a * k^3`. # C++ ``` C++ class Solution { public: int titleToNumber(string s) { int res = 0, multiplier = 1; for(int i = s.size() - 1; i >= 0; i--){ res += (int)(s[i] - 'A' + 1) * multiplier; multiplier *= 26; } return res; } }; ```