Excel Sheet Column Title

Excel Sheet Column Title - Problem

Math String Easy

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
...

Input & Output

Example 1 — Single Letter

$ Input: columnNumber = 1

› Output: "A"

💡 Note: The first column in Excel is labeled 'A'

Example 2 — Double Letter Start

$ Input: columnNumber = 28

› Output: "AB"

💡 Note: After Z (26), comes AA (27), then AB (28)

Example 3 — Large Number

$ Input: columnNumber = 701

› Output: "ZY"

💡 Note: 701 converts to ZY using base-26 conversion with adjustment

Constraints

1 ≤ columnNumber ≤ 2³¹ - 1

Visualization

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Asked in

M Microsoft 35 G Google 25 a Amazon 20 Apple 15

The key insight is treating this as a base-26 conversion with 1-based indexing adjustment. The optimal approach uses mathematical division and modulo operations. Time: O(log₂₆ n), Space: O(log₂₆ n)

Common Approaches

✓ Brute Force Generation

⏱️ Time: O(n) Space: O(1)

Start with empty string and generate each consecutive column title by incrementing like a counter. This simulates the Excel column progression exactly.

Mathematical Conversion

⏱️ Time: O(log₂₆ n) Space: O(log₂₆ n)

Convert the column number to base-26 representation, but adjust for Excel's 1-based indexing by subtracting 1 before each division operation.

Brute Force Generation — Algorithm Steps

Start with first column 'A'
Increment column title one by one
Return title when we reach columnNumber

Visualization

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Step-by-Step Walkthrough

Subtract 1

Adjust for 1-based indexing

Get Letter

Use modulo 26 to get current letter

Divide by 26

Move to next position

Code -

solution.c — C

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

char* solution(int columnNumber) {
    char* result = malloc(10);
    result[0] = '\0';
    char temp[10];
    int pos = 0;
    
    while (columnNumber > 0) {
        columnNumber--;
        temp[pos++] = 'A' + (columnNumber % 26);
        columnNumber /= 26;
    }
    
    for (int i = pos - 1; i >= 0; i--) {
        int len = strlen(result);
        result[len] = temp[i];
        result[len + 1] = '\0';
    }
    
    return result;
}

int main() {
    int columnNumber;
    scanf("%d", &columnNumber);
    
    char* result = solution(columnNumber);
    printf("%s\n", result);
    free(result);
    
    return 0;
}

Time & Space Complexity

Time Complexity

⏱️

O(n)

Must generate n column titles sequentially

⚡ Linearithmic

Space Complexity

O(1)

Only storing current column title string

⚡ Linearithmic Space

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Medium Frequency

~15 min Avg. Time

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Ln 1, Col 1

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Input & Output

Constraints

Visualization

Related Problems

Common Approaches

Brute Force Generation — Algorithm Steps

Visualization

Code -

Time & Space Complexity

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