Generate Tag for Video Caption

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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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

✓ Character-by-Character Processing

⏱️ Time: O(n) Space: O(n)

Iterate through each character, determine if it starts a new word, apply camelCase rules, filter non-letters, and truncate at the end.

Word-Based Processing

⏱️ Time: O(n) Space: O(n)

Split the caption into words using regex or space detection, process each word to create camelCase, filter non-letters, and truncate the result.

Character-by-Character Processing — Algorithm Steps

Step 1: Start with '#' and iterate through each character
Step 2: Track word boundaries and apply camelCase rules
Step 3: Filter out non-English letters and truncate to 100 chars

Visualization

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Step-by-Step Walkthrough

Start with #

Initialize result with hashtag symbol

Process Letters

Extract words and apply camelCase rules

Clean & Truncate

Remove non-letters and limit to 100 chars

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])) {
            // Start of a word
            char word[1000] = "";
            int wordLen = 0;
            while (i < strlen(caption) && isalpha(caption[i])) {
                word[wordLen++] = tolower(caption[i]);
                i++;
            }
            word[wordLen] = '\0';
            
            if (wordLen > 0) {
                if (firstWord) {
                    strcat(result, word);
                    resultLen += wordLen;
                    firstWord = 0;
                } else {
                    word[0] = toupper(word[0]);
                    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 through all characters in the caption

✓ Linear Growth

Space Complexity

O(n)

Result string can be up to 100 characters plus temporary variables

⚡ Linearithmic Space

23.5K Views

Medium Frequency

~15 min Avg. Time

890 Likes

Ln 1, Col 1

Smart Actions

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Input & Output

Constraints

Visualization

Related Problems

Common Approaches

Character-by-Character Processing — Algorithm Steps

Visualization

Code -

Time & Space Complexity

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