Rock Paper Scissors - FreeCodeCamp #139 Daily Challenge

Rock Paper Scissors - Analysis and Explanation

Problem Statement

Given a game of “Rock, Paper, Scissors”, receive two strings representing each player’s choice: “Rock”, “Paper”, or “Scissors”. Determine the result according to the classic rules:

• Rock beats Scissors
• Paper beats Rock
• Scissors beats Paper

Return:

• “Player 1 wins” if player one wins
• “Player 2 wins” if player two wins
• “Tie” if it’s a draw

Initial Analysis

You only need to compare the choices and decide the result. Input validation is not necessary, as all inputs are guaranteed to be valid.

Test Cases

rockPaperScissors('Rock', 'Rock') // "Tie"
rockPaperScissors('Rock', 'Paper') // "Player 2 wins"
rockPaperScissors('Scissors', 'Paper') // "Player 1 wins"
rockPaperScissors('Rock', 'Scissors') // "Player 1 wins"
rockPaperScissors('Scissors', 'Scissors') // "Tie"
rockPaperScissors('Scissors', 'Rock') // "Player 2 wins"

These cover all possible combinations.

Solution Development

Approach

A direct conditional structure is used:

• If both choose the same, it’s a tie.
• If the combination is one of the three where player one wins, return “Player 1 wins”.
• In any other case, player two wins.

Step by Step

1. If player1 === player2 → “Tie”
2. If (player1, player2) is one of:

• (‘Rock’, ‘Scissors’)
• (‘Paper’, ‘Rock’)
• (‘Scissors’, ‘Paper’) → “Player 1 wins”

3. Otherwise, “Player 2 wins”

Final Code

/**
 * FreeCodeCamp: Rock Paper Scissors
 * @param {string} player1 - "Rock", "Paper" or "Scissors"
 * @param {string} player2 - "Rock", "Paper" or "Scissors"
 * @returns {string} Result: "Player 1 wins", "Player 2 wins" or "Tie"
 */
function rockPaperScissors(player1, player2) {
  if (player1 === player2)
    return 'Tie'
  if (
    (player1 === 'Rock' && player2 === 'Scissors')
    || (player1 === 'Paper' && player2 === 'Rock')
    || (player1 === 'Scissors' && player2 === 'Paper')
  ) {
    return 'Player 1 wins'
  }
  return 'Player 2 wins'
}

export default rockPaperScissors

Complexity Analysis

Time

The function is $O(1)$: it only compares strings and evaluates conditionals.

Space

No auxiliary structures are used: $O(1)$.

Edge Cases and Considerations

There are no edge cases beyond those covered, as the inputs are always valid and limited.

Reflections and Learnings

Concepts applied:

• String comparison
• Conditionals
• Game logic