Excel Sheet Column Title Explained

Problem Statement

Given a positive integer n, convert it to its corresponding Excel sheet column title. Excel columns are labeled as A (1), B (2), ..., Z (26), AA (27), AB (28), and so on, resembling a base-26 number system where digits are letters A-Z. This problem tests your ability to handle number-to-string conversion with custom base systems.

Example

Input: n = 28

Output: "AB"

Explanation: 28 corresponds to AA (27) + B (2) = AB.

Code

public class Solution {
    public String convertToTitle(int n) {
        StringBuilder sb = new StringBuilder();
        while (n > 0) {
            n--;
            sb.append((char) ('A' + (n % 26)));
            n /= 26;
        }
        return sb.reverse().toString();
    }

    public static void main(String[] args) {
        Solution sol = new Solution();
        System.out.println(sol.convertToTitle(28)); // "AB"
    }
}
            

def convert_to_title(n):
    result = []
    while n > 0:
        n -= 1
        result.append(chr(ord('A') + (n % 26)))
        n //= 26
    return ''.join(result[::-1])

# Example usage
print(convert_to_title(28))  # "AB"
            

function convertToTitle(n) {
    let result = '';
    while (n > 0) {
        n--;
        result = String.fromCharCode('A'.charCodeAt(0) + (n % 26)) + result;
        n = Math.floor(n / 26);
    }
    return result;
}

// Example usage
console.log(convertToTitle(28)); // "AB"
            

Explanation

• Excel columns use a base-26 system, but 1-based (A=1, not 0).
• Subtract 1 from n to adjust to 0-based for modulo and division.
• Extract the remainder modulo 26 to get the current letter (0=A, 1=B, ..., 25=Z).
• Divide n by 26 to process the next digit.
• Reverse the result since digits are computed from least to most significant.

Note