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
**Credits:**Special thanks to [@ifanchu](https://leetcode.com/discuss/user/ifanchu) for adding this problem and creating all test cases.
题意：把数字转换成字母，就好像是一个进制的转换问题。
java代码：
class Solution {
public String convertToTitle(int n) {
StringBuilder builder = new StringBuilder();
for (; n != 0; n = (n - 1) / 26) {
char c = (char)(n % 26 + 64);
if (c == 64) c = 90;
builder.append(c);
}
builder.reverse();
return new String(builder);
}
}
