First Letter Capitalization - Practice Coding Problems

First Letter Capitalization - Problem

Database Hard

You are working as a data engineer for a content management system that needs to standardize text formatting across their database. Your task is to create a title case transformation function that capitalizes the first letter of each word while converting all other letters to lowercase.

Given a table user_content with columns content_id and content_text, you need to:

Capitalize the first letter of each word
Convert all other letters to lowercase
Preserve all existing spaces exactly as they are
Return both the original text and the transformed text

The challenge lies in handling various edge cases like multiple consecutive spaces, mixed-case words, and all-caps text. This is commonly needed for cleaning user-generated content, standardizing titles, or preparing text for display.

Note: The input contains only alphabetic characters and spaces - no special characters or punctuation.

Input & Output

example_1.py — Basic Mixed Case

$ Input: content_text = "hello world of SQL"

› Output: "Hello World Of Sql"

💡 Note: Each word's first letter is capitalized: 'hello' → 'Hello', 'world' → 'World', 'of' → 'Of', 'SQL' → 'Sql'. All other letters are converted to lowercase.

example_2.py — All Caps Conversion

$ Input: content_text = "the QUICK brown fox"

› Output: "The Quick Brown Fox"

💡 Note: The all-caps word 'QUICK' is converted to title case 'Quick'. Mixed case words like 'the' and 'brown' are properly capitalized, while 'fox' gets its first letter capitalized.

example_3.py — Multiple Spaces

$ Input: content_text = "data science AND"

› Output: "Data Science And"

💡 Note: Multiple consecutive spaces are preserved exactly as they appear. Each word boundary is correctly identified regardless of space count: 'data' → 'Data', 'science' → 'Science', 'AND' → 'And'.

Constraints

1 ≤ content_text.length ≤ 1000
content_text contains only alphabetic characters and spaces
No leading or trailing spaces guaranteed, but may exist
Multiple consecutive spaces may exist and must be preserved

Visualization

Tap to expand

Understanding the Visualization

Initialize State

Start with word_start = true, ready to capitalize the first character

Process Characters

For each character: if space, preserve and set word_start = true; if letter and word_start, capitalize and set word_start = false; if letter and not word_start, make lowercase

Build Result

Append each processed character to build the final title-case string

Complete

Return the transformed string with proper title case formatting

Key Takeaway

🎯 Key Insight: By treating this as a simple two-state machine, we can process the entire string in a single pass while correctly handling all capitalization rules and preserving spaces.

Asked in

f Meta 35 G Google 28 ⊞ Microsoft 22 a Amazon 18

The optimal solution uses a single pass approach with a boolean flag to track word boundaries. By maintaining a word_start state that toggles between true (at word start) and false (within word), we can efficiently capitalize first letters and lowercase others in O(n) time and O(1) extra space. This eliminates the need for backward scanning or multiple passes while correctly handling all edge cases including multiple spaces.

Common Approaches

Approach	Time	Space	Notes
✓ Character-by-Character with Boundary Check	O(n²)	O(1)	Check each character and scan backwards to determine if it's at word start
Single Pass with State Tracking (Optimal)	O(n)	O(1)	Track word boundaries using a boolean flag in one efficient pass

Character-by-Character with Boundary Check — Algorithm Steps

Iterate through each character in the string
For each alphabetic character, scan backwards to find word boundary
If it's the first character of a word, capitalize it
Otherwise, convert to lowercase
Preserve all space characters as-is

Visualization

Tap to expand

Step-by-Step Walkthrough

Start Processing

Begin at first character 'h' in 'hello'

Check Boundary

Scan backwards - no previous characters, so it's word start

Capitalize

Convert 'h' to 'H' since it starts a word

Continue

For 'e', scan back and find 'h' (letter), so lowercase it

Code -

solution.c — C

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

char* titleCaseTransform(const char* contentText) {
    if (!contentText || strlen(contentText) == 0) {
        return NULL;
    }
    
    int len = strlen(contentText);
    char* result = (char*)malloc((len + 1) * sizeof(char));
    
    for (int i = 0; i < len; i++) {
        char ch = contentText[i];
        if (ch == ' ') {
            result[i] = ch;
        } else if (isalpha(ch)) {
            // Check if this is the start of a word by looking backwards
            int isWordStart = 1;
            int j = i - 1;
            while (j >= 0) {
                if (contentText[j] == ' ') {
                    j--;
                    continue;
                } else if (isalpha(contentText[j])) {
                    isWordStart = 0;
                    break;
                } else {
                    break;
                }
            }
            
            if (isWordStart) {
                result[i] = toupper(ch);
            } else {
                result[i] = tolower(ch);
            }
        } else {
            result[i] = ch;
        }
    }
    
    result[len] = '\0';
    return result;
}

int main() {
    const char* testCases[][2] = {
        {"1", "hello world of SQL"},
        {"2", "the QUICK brown fox"},
        {"3", "data science AND machine learning"},
        {"4", "TOP rated programming BOOKS"}
    };
    
    for (int i = 0; i < 4; i++) {
        char* converted = titleCaseTransform(testCases[i][1]);
        printf("ID: %s, Original: \"%s\", Converted: \"%s\"\n", 
               testCases[i][0], testCases[i][1], converted);
        free(converted);
    }
    
    return 0;
}

Time & Space Complexity

Time Complexity

⏱️

O(n²)

For each character, we might scan back to the beginning to find word boundary

⚠ Quadratic Growth

Space Complexity

O(1)

Only using a constant amount of extra space for the result string

✓ Linear Space

24.7K Views

Medium Frequency

~15 min Avg. Time

847 Likes

Ln 1, Col 1

Smart Actions

💡 Explanation

AI Ready

💡 Suggestion Tab to accept Esc to dismiss

// Output will appear here after running code

Code Editor Closed

Click the red button to reopen

Input & Output

Constraints

Visualization

Related Problems

Common Approaches

Character-by-Character with Boundary Check — Algorithm Steps

Visualization

Code -

Time & Space Complexity

Select Compiler