Excel Sheet Column Title & Excel Sheet Column Number

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 

注意，这题的数字不是从0开始，而是从1开始，我开始的时候用10进制的方式进行转换，发现不对。所以在程序里，用了n - 1.

　　public String convertToTitle(int n) {
        StringBuilder sb = new StringBuilder();
        while (n > 0) {
            int temp = (n - 1) % 26;
            sb.insert(0, (char)(temp  + 'A'));
            n = (n - 1) / 26;
        }
        return sb.toString();
    }

Excel Sheet Column Number

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 

public class Solution {
    public int titleToNumber(String s) {
        // s = "AB";
        int total = 0;
        for (int i = 0; i < s.length(); i++) {
            total = total * 26 + s.charAt(i) - 'A' + 1;
        }
        return total;
    }
}