leetcode:171 Excel Sheet Column Number－每日編程第十題

Excel Sheet Column Number

Total Accepted: 54683 Total Submissions: 140674 Difficulty: Easy

 

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 
思路：
假設num是一個五位數ABCDE.
num=A*26^4+B*26^3+c*26^2+D*26+E*1;
radix作爲基數，初始化爲1,每次循環*26;

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