Excel Sheet Column Title

 Given an integer columnNumber, return its corresponding column title as it appears in an Excel sheet.


For example:


A -> 1

B -> 2

C -> 3

...

Z -> 26

AA -> 27

AB -> 28 

...

 


Example 1:


Input: columnNumber = 1

Output: "A"

Example 2:


Input: columnNumber = 28

Output: "AB"

Example 3:


Input: columnNumber = 701

Output: "ZY"


💡 Key Concepts Recap:

  • columnNumber--: Shift from 1-based to 0-based

  • % 26: To find the current letter

  • 'A' + remainder: To convert number to character

  • insert(0, letter): To build the result from back to front

  • / 26: Move to the next "digit" (letter)


class Solution {
    public String convertToTitle(int columnNumber) {
       
         StringBuilder result = new StringBuilder();

        while (columnNumber > 0) {
            columnNumber--; // Step 1: shift to 0-based
            int remainder = columnNumber % 26; // Step 2: get letter index
            char letter = (char) ('A' + remainder); // Step 3: get letter
            result.insert(0, letter); // Step 4: insert at beginning
            columnNumber /= 26; // Step 5: move to next letter
        }

        return result.toString();
    }
}

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