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 
    ...

Example 1:

Input: 1
Output: "A"

Example 2:

Input: 28
Output: "AB"

Example 3:

Input: 701
Output: "ZY"

class Solution {
    public String convertToTitle(int n) {
        List<Character> list = new ArrayList();
        Stack<Character> stack = new Stack();
        for(char c = 'A'; c <= 'Z'; c++) list.add(c);
        while(n != 0){
            n--;
            char k = list.get(n % 26 );
            //System.out.println(k);
            stack.push(k);
            n = n / 26;
        }
        StringBuilder sb = new StringBuilder();
        while(!stack.isEmpty()) sb.append(stack.pop());
        return sb.toString();
    }
}

有病？？

注意因为是0-index的list，所以n进去要先减一

class Solution {
    public String convertToTitle(int n) {
        String ret = "";
        while (n != 0) {
            ret = (char)('A'+(--n)%26) + ret;
            n /= 26;
        }
        return ret;
    }
}