JavaScript Coding Test Course, Making Cocktails

In this course, we will cover coding test problems using JavaScript.
In particular, we will solve various algorithm problems with the theme
of making cocktails. The problem we will discuss today is “Making Cocktails from Subset Combinations.”

Problem Description

We need to find all possible combinations of cocktails using the given ingredients.
Each cocktail must consist of two or more ingredients, and
the combinations should be presented without duplicates.

Input

  • Number of ingredients N (1 ≤ N ≤ 20)
  • Array of strings ingredients containing the names of each ingredient

Output

Should return an array of all possible cocktail combinations. Each combination should
be represented in the form ["ingredient1", "ingredient2", ...],
and the ingredients in each combination must be sorted in alphabetical order.

Example

Input

const ingredients = ["vodka", "orange juice", "grenadine"];

Output

[["grenadine", "orange juice"], ["grenadine", "vodka"], ["orange juice", "vodka"], ["grenadine", "orange juice", "vodka"]]

Problem Solving Process

To solve this problem, we first need to think about how to create all possible combinations.
We can solve the problem using recursive functions or bit manipulation for combination generation.

Algorithm Design

We will use a recursive approach to generate cocktail combinations.
The main steps of the algorithm are as follows:

  1. Sort the ingredient array. (This is to produce the output in sorted order)
  2. Use a recursive function to generate combinations of ingredients.
  3. If the combination consists of two or more ingredients, add it to the result array.

Code Implementation

Now we will implement the algorithm we designed in JavaScript. 

function cocktailCombinations(ingredients) {
    const result = [];
    
    ingredients.sort();

    const generateCombinations = (start, currentCombination) => {
        if (currentCombination.length > 1) {
            result.push([...currentCombination]);
        }

        for (let i = start; i < ingredients.length; i++) {
            currentCombination.push(ingredients[i]);
            generateCombinations(i + 1, currentCombination);
            currentCombination.pop();
        }
    };

    generateCombinations(0, []);

    return result;
}

// Example usage
const ingredients = ["vodka", "orange juice", "grenadine"];
console.log(cocktailCombinations(ingredients));

Code Explanation

The above cocktailCombinations function takes an array of ingredients as input
and generates all possible cocktail combinations. It defines and calls an internal
recursive function called generateCombinations to generate the combinations.

Detailed Functions

  • Ingredient Sorting: Sorts the input ingredients to maintain consistency in the output.
  • Recursive Calls: Uses recursion to select each ingredient and explore combination possibilities.
  • Add Combination: Only adds to the result if the current combination length is 2 or more.

Complexity Analysis

The time complexity of this algorithm is
O(2^N).
This is because it is a binary choice problem, deciding whether to select each ingredient, which
is equal to the maximum number of physically possible combinations when exploring all combinations.
The space complexity is proportional to the depth of the array, and in the worst case, the
additional memory used will depend on the number of combinations.

Test Cases

Let’s test the function with various inputs to verify its accuracy. 

// Test cases
const test1 = ["gin", "tonic", "lime"];
const test2 = ["whiskey", "soda", "angostura", "lemon"];
const test3 = [];

// Output results
console.log(cocktailCombinations(test1)); // [["gin", "lime"], ...]
console.log(cocktailCombinations(test2)); // ...
console.log(cocktailCombinations(test3)); // []

Conclusion

In this course, we have gone through the process of solving the cocktail combination problem using
JavaScript. Through a deep understanding of arrays, recursion, and combination possibilities,
we are able to more effectively learn strategies to deal with common
problem types encountered in coding tests.

Additional Information

In actual coding tests, there may often be additional exception handling or input constraint requirements.
Reflecting these conditions to improve the code will also be good practice.
Since the process of adding various features tailored to individual circumstances is important,
we hope this problem will create opportunities for you to advance further.