LeetCode: 171. Excel Sheet Column Number

题目描述

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

解题思路

进制转换。这实际上是将 26 进制转换为 10 进制。

AC 代码

class Solution {
public:
    int titleToNumber(string s) {
        int num = 0;
        for(auto iter = s.begin(); iter != s.end(); ++iter)
        {
            num = num * 26 + (*iter -'A' + 1);
        }
        return num;
    }
};