Excel Sheet Column Number

171. Excel Sheet Column Number

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Problem

Related to question Excel Sheet Column Title

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

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问题

给定一个像Excel表单一样列标题，将其转化为数字。
例如：

A -> 1
B -> 2
C -> 3
…
Z -> 26
AA -> 27
AB -> 28

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思路

本题本质上是二十六进制转十进制数，与二进制转十进制类似。

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代码（C++）

class Solution {
public:
    int titleToNumber(string s) {
        int length = s.length();
        int number = 0;
        for (int i = 0;i<length-1;i++)
        {
            number = (number + s[i]-'A'+1)*26;
        }
        number += (s[length -1]-'A'+1);
        return number;
    }
};

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运行结果