JavaScript Coding Test Course, Find Minimum Value 2

In this tutorial, we will take a detailed look at how to solve employment-related algorithm problems using JavaScript. This article will address the ‘Find Minimum 2’ problem, explaining the approach to problem-solving, step-by-step processes, and optimization methods.

Problem Description

The following problem involves finding the minimum value that satisfies specific conditions in an array. For the given array, the following conditions apply:

  • An array consisting of positive integers is given.
  • Only the elements at odd indices of the array should be considered to find the minimum value.
  • If a minimum value cannot be found, it should return `null`.

Example of the Problem

            Input: [5, 3, 4, 1, 2, 7, 6]
            Output: 1

            Input: [2, 9, 6, 7, 10]
            Output: 9

            Input: [4, 4, 4, 4]
            Output: null

Approach to Solve the Problem

To solve this problem, we follow these steps:

  1. Extract only the elements at odd indices from the input array.
  2. Find the minimum value among the extracted elements.
  3. If a minimum value exists, return it; otherwise, return `null`.

Step 1: Extract Odd Index Elements

To extract elements at odd indices, we can use the `filter` method. This method returns an array of elements that satisfy a given condition.

Step 2: Find the Minimum Value

There are several ways to find the minimum value from the array extracted from odd indices. Using the `Math.min` function allows for straightforward minimum value retrieval.

Step 3: Return the Result

After finding the minimum value, we add logic to return it or `null` based on the condition.

Code Implementation for Problem Solving

Now, based on these processes, let’s write JavaScript code to solve the problem. Below is the code that implements the algorithm described above:

            function findMinOddIndex(arr) {
                // Extracting odd index elements
                const oddIndexedElements = arr.filter((_, index) => index % 2 === 1);

                // Return null if there are no odd index elements
                if (oddIndexedElements.length === 0) {
                    return null;
                }

                // Return the minimum value
                return Math.min(...oddIndexedElements);
            }

            // Example tests
            console.log(findMinOddIndex([5, 3, 4, 1, 2, 7, 6])); // 1
            console.log(findMinOddIndex([2, 9, 6, 7, 10])); // 9
            console.log(findMinOddIndex([4, 4, 4, 4])); // null

Code Explanation

The above code works as follows:

  • The function `findMinOddIndex` takes the input array and filters out the elements corresponding to odd indices.
  • If the filtered result is an empty array, meaning there are no elements at odd indices, it returns `null`.
  • If not, it calculates and returns the minimum value using `Math.min`.

Testing and Verifying Results

Let’s run various test cases with the code we wrote. We will check the execution results to ensure the correct outcomes are returned.

  • Input: [5, 3, 4, 1, 2, 7, 6] → Output: 1
  • Input: [2, 9, 6, 7, 10] → Output: 9
  • Input: [4, 4, 4, 4] → Output: null
  • Input: [] → Output: null
  • Input: [0, -1, 3, -5, 4] → Output: -5 (the minimum value among -1 and -5 at odd indices)

Performance Optimization

The performance of the currently implemented code is good, with an average time complexity of O(n). However, if the array size is very large, we can further optimize performance. For example, we can use a single iteration to find the minimum value at odd indices. Below is an example of this implementation:

            function findMinOddIndexOptimized(arr) {
                let min = Infinity;

                for (let i = 1; i < arr.length; i += 2) {
                    if (arr[i] < min) {
                        min = arr[i];
                    }
                }

                return min === Infinity ? null : min;
            }

            // Example tests
            console.log(findMinOddIndexOptimized([5, 3, 4, 1, 2, 7, 6])); // 1
            console.log(findMinOddIndexOptimized([2, 9, 6, 7, 10])); // 9
            console.log(findMinOddIndexOptimized([4, 4, 4, 4])); // null

Conclusion

In this tutorial, we learned how to find the minimum value at odd indices in a given array using JavaScript. Clearly understanding the requirements of the problem, and deriving the optimal solution through an efficient algorithm is a crucial skill in coding tests. While filtering and mapping arrays can easily solve problems, optimization with performance in mind is also necessary.

In your practice for upcoming coding tests, I hope you get familiar with solving similar pattern problems repeatedly. Additionally, attempting various variations of problems can help enhance your problem-solving abilities.