LeetCode171 Excel Sheet Column Number

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

题源：here；完整实现：here

思路：

这道题本质上是将26进制转换位10进制，我们只需要以为乘上相应的权值就行了。

class Solution {
public:
	int titleToNumber(string s) {
		int res = 0;
		for (auto i : s) {
			res = res * 26 + (i - 'A' + 1);
		}
		return res;
	}
};