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
剛開(kāi)始知道需要mod 26 但沒(méi)反應(yīng)過(guò)來(lái) 要n-1 .。。。

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
剛開(kāi)始知道需要mod 26 但沒(méi)反應(yīng)過(guò)來(lái) 要n-1 .。。。