leetcode 171

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 

从A到Z依次代表从1到26，按照26进制进位。
代码如下：

class Solution {
public:
    int titleToNumber(string s) {
        int n = s.length();
        int m = n;
        int result = 0;
        if(n == 0)
        {
            return 0;
        }
        result = (int)s[m-1];
        result -= 64;
        for(int i = 1; i < n+1; i++)
        {
            m--;
            if(m == 0)
            {
                return result;
            }
            int p = 1;
            for(int j = 0; j < i; j++)
            {
                p *= 26;
            }
            int re = (int)s[m-1];
            re -= 64;
            result = result + re * p;
        }
        return result;
    }
};