leetcode:171 Excel Sheet Column Number－每日编程第十题

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：假设num是一个五位数ABCDE.num=A*26^4+B*26^3+c*26^2+D*26+E*1;radix作为基数，初始化为1,每次循环*26;

 1 class Solution {
 2 public:
 3     int titleToNumber(string s) {
 4         int len=s.length();
 5         if(len==0){
 6             return 0;
 7         }
 8         int num=0;
 9         int radix=1;
10         for(int i=len-1;i>=0;i--){
11             num+=radix*(s[i]-‘A‘+1);
12             radix*=26;
13         }
14         return num;
15     }
16 };