LeetCode No.171 Excel Sheet Column Number

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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題目鏈接：https://leetcode.com/problems/excel-sheet-column-number/

題目大意：求出用A-Z表示的26進制數的原值。

思路：模擬26進制的生成的模式生成原來的值。（參考第168題）

參考代碼：

class Solution {
public:
    int titleToNumber(string s) {
        int n = s.size() ;
        if ( n == 0 )
            return 0 ;
        int ans = 0 , power = 1 ;
        for ( int i = n - 1 ; i >= 0 ; i -- )
        {
            ans += ( ( s[i] - 'A' ) + 1 ) * power ;
            power *= 26 ;
        }
        return ans ;
    }
};