Hackerrank: Understanding the minMaxSum Function in JavaScript

Introduction:

In the world of programming, finding the minimum and maximum values in an array and calculating the sum of all elements between those values is a common task. It's not only an interesting algorithmic challenge but also has practical applications. In this article, we will explore a JavaScript function called minMaxSum, which does exactly that. We will dissect the code and understand how it works step by step.

The minMaxSum Function:

Let's start by examining the code snippet of the minMaxSum function:

function miniMaxSum(arr) {
    let max = arr[0];
    let min = arr[0];
    for(let val = 0; val < arr.length; val++) {
        if(arr[val] > max) {
            max = arr[val];
        } else if(arr[val] < min) {
            min = arr[val];
        }
    }

    let maxValIndex = arr.indexOf(max);
    let minValIndex = arr.indexOf(min);

    let minSumList = [];
    let maxSumList = [];

    if(min === max) {
        for(let i = 0; i < arr.length - 1; i++) {
            minSumList.push(arr[i]);
            maxSumList.push(arr[i]);
        }
    } else {
        for(let i = 0; i < arr.length; i++) {
            if(arr[i] !== arr[maxValIndex]) {
                minSumList.push(arr[i]);
            }
            if(arr[i] !== arr[minValIndex]) {
                maxSumList.push(arr[i]);
            }
        }
    }

    let minSum = minSumList.reduce((prev, cur) => prev + cur, 0);
    let maxSum = maxSumList.reduce((prev, cur) => prev + cur, 0);
    console.log(`${minSum} ${maxSum}`);
}

How the minMaxSum Function Works:

Now, let's break down the code to understand its functionality step by step:

Initialization:

The function takes an array arr as its input, which contains a list of numbers.
It initializes two variables, max and min, with the first element of the array (arr[0]) to have starting values for comparison.

1. Finding the Maximum and Minimum:

It then loops through the entire array, comparing each element with the current values of max and min.
If an element is greater than the current max, it updates max. If it's smaller than the current min, it updates min.

2. Finding Indexes:

After finding the max and min, it determines their positions in the original array using the indexOf method.

3. Preparing Lists:

The function initializes two arrays, minSumList and maxSumList, which will be used to store the elements for calculating the minimum and maximum sums.

4. Filling Lists:

It then checks if min is equal to max. If they are equal, it means all elements in the array are the same, and it populates both minSumList and maxSumList with all elements except the last one.
If min and max are not equal, it iterates through the array and populates minSumList with all elements except the one that matches the index of max. Similarly, it populates maxSumList with all elements except the one that matches the index of min.

5. Calculating Sums:

It calculates the sum of elements in minSumList and maxSumList using the reduce function.

6. Printing the Results:

Finally, it logs the minimum and maximum sums to the console.
Conclusion:
The minMaxSum function is a clever way to find the minimum and maximum sums of elements in an array. It demonstrates how to efficiently handle edge cases and perform array manipulations in JavaScript, providing valuable insights into array handling and conditional logic. This code is a useful tool for anyone working with arrays and data processing in JavaScript.