Generate Tag for Video Caption - Practice Coding Problems

Generate Tag for Video Caption - Problem

String Simulation Easy

You are given a string caption representing the caption for a video. You need to generate a valid tag for the video by performing the following actions in order:

1. Combine all words into a single camelCase string prefixed with '#'. A camelCase string is one where the first letter of all words except the first one is capitalized, and all other characters are lowercase.

2. Remove all non-English letters except the first '#' character.

3. Truncate the result to a maximum of 100 characters.

Return the generated tag after performing these operations on the caption.

Input & Output

Example 1 — Basic Case

$ Input: caption = "Hello World!"

› Output: #helloWorld

💡 Note: Words are 'Hello' and 'World'. First word becomes lowercase 'hello', second becomes 'World'. Result: '#helloWorld'

Example 2 — With Numbers and Symbols

$ Input: caption = "Coding123 is FUN!!!"

› Output: #codingIsFun

💡 Note: Extract words 'Coding', 'is', 'FUN'. Apply camelCase: 'coding' + 'Is' + 'Fun' = '#codingIsFun'

Example 3 — Single Word

$ Input: caption = "AWESOME"

› Output: #awesome

💡 Note: Single word 'AWESOME' becomes lowercase 'awesome' as the first word. Result: '#awesome'

Constraints

1 ≤ caption.length ≤ 10⁵
caption consists of English letters, digits, spaces, and punctuation marks

Visualization

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Understanding the Visualization

Input

Raw caption with mixed characters, punctuation, numbers

Extract & Transform

Find words, apply camelCase, remove non-letters

Output

Clean hashtag with proper formatting and length limit

Key Takeaway

🎯 Key Insight: Extract words first, then apply formatting rules systematically - much cleaner than processing character by character

Asked in

M Meta 25 T Twitter 30 T TikTok 20 I Instagram 15

The key insight is to extract words first, then apply camelCase rules systematically. The word-based approach is cleaner than character-by-character processing. Time: O(n), Space: O(n)

Common Approaches

Approach	Time	Space	Notes
✓ Word-Based Processing	O(n)	O(n)	Split into words first, then process each word for camelCase formatting
Character-by-Character Processing	O(n)	O(n)	Process each character individually, tracking word boundaries and case rules

Word-Based Processing — Algorithm Steps

Step 1: Extract all words containing letters from the caption
Step 2: Convert first word to lowercase, capitalize subsequent words
Step 3: Combine with '#' prefix and truncate to 100 characters

Visualization

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Step-by-Step Walkthrough

Extract Words

Find all letter sequences in the caption

Apply camelCase

First word lowercase, others capitalized

Combine & Truncate

Join with # prefix and limit length

Code -

solution.c — C

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

char* solution(char* caption) {
    char* result = (char*)malloc(101 * sizeof(char));
    strcpy(result, "#");
    int resultLen = 1;
    int firstWord = 1;
    int i = 0;
    
    while (i < strlen(caption)) {
        if (isalpha(caption[i])) {
            // Extract word
            char word[1000] = "";
            int wordLen = 0;
            while (i < strlen(caption) && isalpha(caption[i])) {
                word[wordLen++] = caption[i];
                i++;
            }
            word[wordLen] = '\0';
            
            // Process word for camelCase
            if (firstWord) {
                for (int j = 0; j < wordLen; j++) {
                    word[j] = tolower(word[j]);
                }
                firstWord = 0;
            } else {
                word[0] = toupper(word[0]);
                for (int j = 1; j < wordLen; j++) {
                    word[j] = tolower(word[j]);
                }
            }
            
            strcat(result, word);
            resultLen += wordLen;
        } else {
            i++;
        }
    }
    
    // Truncate to 100 characters
    if (resultLen > 100) {
        result[100] = '\0';
    }
    return result;
}

int main() {
    char caption[10000];
    fgets(caption, sizeof(caption), stdin);
    caption[strcspn(caption, "\n")] = 0;
    char* result = solution(caption);
    printf("%s\n", result);
    free(result);
    return 0;
}

Time & Space Complexity

Time Complexity

⏱️

O(n)

Single pass to extract words plus processing each character once

✓ Linear Growth

Space Complexity

O(n)

Store extracted words and result string, both bounded by input length

⚡ Linearithmic Space

23.5K Views

Medium Frequency

~15 min Avg. Time

890 Likes

Ln 1, Col 1

Smart Actions

💡 Explanation

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Input & Output

Constraints

Visualization

Related Problems

Common Approaches

Word-Based Processing — Algorithm Steps

Visualization

Code -

Time & Space Complexity

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