168 - Excel Sheet Column Title

Given a positive integer, return its corresponding column title as appear in an Excel sheet.

For example:

    1 -> A

    2 -> B

    3 -> C

    ...

    26 -> Z

    27 -> AA

    28 -> AB 

Solution： 由于A->1,  计算s的末尾时需先减去1

 class Solution {

 public:

     string convertToTitle(int n) {

         string s;

         while(n){

             s =  (char)('A'+(n-)%)+s;

             n = (n-)/;

         }

         return s;

     }

 };

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 

Solution：26进制转十进制,AAA=27*26+1

1 class Solution {

2 public:

3     int titleToNumber(string s) {   //runtime:8ms

4         int ret=0;

5         for(int i=0;i<s.size();i++)ret = ret*26+s[i]-'A'+1;

6         return ret;

7     }

8 };