Ramiro N. Cosa

Snowflake Generator - FreeCodeCamp #137 Daily Challenge

2 min

Problem Statement

Given a multiline string (separated by \n), return a new string where each line is concatenated with its horizontally mirrored version (reversed character by character, including spaces). Do not modify or remove any spaces or line breaks.

Example:

Input: "_ \n _\n* " (visualized as)


*
 *
*

Expected output: "* _\n ** \n_ *" (visualized as)

*  *
 **
*  *

Initial Analysis

What does the challenge ask?

  • Take a string with line breaks (\n) representing a pattern.
  • For each line, create its horizontal mirror (reverse all characters, including spaces).
  • Concatenate the original line with its mirror, without modifying spaces or line breaks.

Key Test Cases

  • Input: "_ \n _\n* " → Output: "* _\n ** \n_ *"
  • Input: "X=~" → Output: "X=~~=X"
  • Input: " X \n v \nX--=\n ^ \n X " → Output: " X X \n v v \nX--==--X\n ^ ^ \n X X "
  • Input: "* _\n _ _ \n_ * _\n _ _ \n_ _" → Output: "_ ** _\n _ * * _ \n_ * ** * _\n _ * * _ \n_ ** *"
  • Input: "_ -\n _ -\n* -" → Output: "* -- _\n _ -- _ \n_ -- *"

These cover patterns with different characters, spaces, and line lengths.

Strategy

  1. Split the string into lines: Use split('\n').
  2. Mirror each line: Reverse with split(''), reverse(), join('').
  3. Concatenate original and mirror: For each line, join original + mirror.
  4. Rebuild the final string: Join with join('\n').

This preserves formatting and spaces.

Implementation

/**
 * FreeCodeCamp Problem: Snowflake Generator
 * @param {string} crystals - Multiline snowflake pattern string
 * @returns {string} String with each line mirrored and concatenated
 */
function generateSnowflake(crystals) {
  const lines = crystals.split('\n')
  return lines
    .map(line => line + line.split('').reverse().join(''))
    .join('\n')
}
export default generateSnowflake

Complexity Analysis

  • Time: If nn is the number of lines and mm is the maximum line length, complexity is O(n⋅m)O(n \cdot m).
  • Space: Also O(n⋅m)O(n \cdot m), since each line is duplicated.

Edge Cases and Considerations

  • Empty lines: Duplicated correctly.
  • Spaces: All spaces are preserved, even at the start/end.
  • No line breaks: Treated as a single line and mirrored.
  • Special characters: Mirrored as-is, no restrictions.

Reflections and Learnings

  • String and array manipulation in JavaScript.
  • Key methods: split, reverse, join.
  • Importance of respecting formatting and spaces in text problems.

Resources

freecodecamp daily-challenge