# LeetCode – Excel Sheet Column Title (Java)

Problem

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
```

Java Solution

This problem is the reverse version of Excel Sheet Column Number.

The key is `n--`. The minimum in 26-bit number is mapped to 1, not 0.

```public String convertToTitle(int n) { if(n <= 0){ throw new IllegalArgumentException("Input is not valid!"); }   StringBuilder sb = new StringBuilder();   while(n > 0){ n--; char ch = (char) (n % 26 + 'A'); n /= 26; sb.append(ch); }   sb.reverse(); return sb.toString(); }```
Category >> Algorithms >> Interview >> Java
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• Ankit

Good solution.Only just correct
s=String.valueOf((char)(n%26+’A’))+s;

• Arjun Dubashi

You use a string builder because string concantenation operates in O(N^2) time

• m00dy

Noob

• Anna Kulik

There is no need to use a StringBuilder.
``` string s = ""; while(n>0) { n--; s = ((char)(n%26 +'A')).ToString() + s; n/=26; } return s; ```
Leetcode accepted this.
Thank you for the simple solution!