Excel Sheet Column Number - Practice Coding Problems

Excel Sheet Column Number - Problem

Math String Easy

Ever wondered how Excel magically converts column titles like A, B, AA, ZY into numbers behind the scenes? Here's your chance to decode the mystery!

Given a string columnTitle that represents the column title as it appears in an Excel sheet, return its corresponding column number.

Think of it as a base-26 number system where:

A → 1
B → 2
C → 3
...
Z → 26
AA → 27
AB → 28
...

Your task is to convert any valid Excel column title into its numeric equivalent.

Input & Output

example_1.py — Single Character

$ Input: columnTitle = "A"

› Output: 1

💡 Note: A is the first column, so it corresponds to 1

example_2.py — Two Characters

$ Input: columnTitle = "AB"

› Output: 28

💡 Note: AB = A×26 + B = 1×26 + 2 = 28. After Z(26), we get AA(27), then AB(28)

example_3.py — Boundary Case

$ Input: columnTitle = "ZY"

› Output: 701

💡 Note: ZY = Z×26 + Y = 26×26 + 25 = 676 + 25 = 701

Constraints

1 ≤ columnTitle.length ≤ 7
columnTitle consists only of uppercase English letters
columnTitle is in the range ["A", "FXSHRXW"]

Visualization

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Understanding the Visualization

Understand the Pattern

A=1, B=2, ..., Z=26, AA=27, AB=28, ...

Apply Base-26 Logic

Each position represents a power of 26

Calculate from Left to Right

Multiply by 26 and add current character value

Get Final Result

The accumulated value is our answer

Key Takeaway

🎯 Key Insight: Excel columns use a bijective base-26 system where each position represents powers of 26, but with 1-based indexing instead of 0-based.

Asked in

⊞ Microsoft 45 G Google 32 a Amazon 28 f Meta 15

The optimal approach treats the Excel column title as a base-26 number system where A=1, B=2, ..., Z=26. We iterate through each character from left to right, multiply our current result by 26, and add the current character's value. This gives us O(n) time complexity and O(1) space complexity, making it both simple and efficient.

Common Approaches

Approach	Time	Space	Notes
✓ Character-by-Character Conversion	O(n)	O(1)	Process each character individually with manual position calculation

Character-by-Character Conversion — Algorithm Steps

Initialize result to 0
For each character from left to right
Convert character to number (A=1, B=2, ..., Z=26)
Multiply current result by 26 and add the character value
Return the final result

Visualization

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Step-by-Step Walkthrough

Initialize

Start with result = 0

Process 'A'

A = 1, result = 0 × 26 + 1 = 1

Process 'B'

B = 2, result = 1 × 26 + 2 = 28

Final Result

AB = 28

Code -

solution.c — C

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

int titleToNumber(char* columnTitle) {
    int result = 0;
    int len = strlen(columnTitle);
    for (int i = 0; i < len; i++) {
        // Convert A=1, B=2, ..., Z=26
        int charValue = columnTitle[i] - 'A' + 1;
        // Build result as base-26 number
        result = result * 26 + charValue;
    }
    return result;
}

int main() {
    char columnTitle[10];
    scanf("%s", columnTitle);
    // Remove quotes if present
    if (columnTitle[0] == '"') {
        int len = strlen(columnTitle);
        for (int i = 0; i < len-2; i++) {
            columnTitle[i] = columnTitle[i+1];
        }
        columnTitle[len-2] = '\0';
    }
    printf("%d\n", titleToNumber(columnTitle));
    return 0;
}

Time & Space Complexity

Time Complexity

⏱️

O(n)

We need to process each character exactly once, where n is the length of the column title

✓ Linear Growth

Space Complexity

O(1)

Only using a few variables to store the result and current character value

✓ Linear Space

89.5K Views

Medium Frequency

~12 min Avg. Time

2.2K Likes

Ln 1, Col 1

Smart Actions

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Input & Output

Constraints

Visualization

Related Problems

Common Approaches

Character-by-Character Conversion — Algorithm Steps

Visualization

Code -

Time & Space Complexity

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