JavaScript program to find element at given index after multiple rotations

We will implement a JavaScript program to find the element at a given index after multiple rotations. This program will ask us to perform a rotation on the array and then return the element present at the specified index. To accomplish this task, we will use the modulo operator to calculate the new index after each rotation. The future continuous tense will be used throughout the explanation.

In the program, we will get the input, rotation number and index of the array. We will then perform rotations using the modulo operator to find the new index after each rotation. The new index is found by adding the number of rotations to the original index and then taking the sum modulo the array length. The element at the final index will be returned as the result of the program.

In summary, we will develop a simple yet efficient program to find the element at a given index after multiple rotations. This program demonstrates the use of the modulo operator and is a valuable tool for anyone wishing to perform array rotations in JavaScript.

method

Given an array of elements and multiple rotations k, the task is to find the element at the given index n after the rotation.

• First, determine the actual position of the element after k rotations. The actual position can be found by taking modulo n and k.

• Performs a rotation on the array by moving the elements k times to the right.

• In order to achieve rotation, we can use the following method -

• Store the last element in a temporary variable.

• Move all elements one step to the right.

• Replace the first element with a temporary variable.

• Repeat step 3 k times to complete all spins.

• After all rotations are completed, return the element at the nth index, which is the actual position now.

• The time complexity of this method is O(n * k), , where n is the number of elements in the array. However, it can be optimized to O(n) by using the concept of cyclic rotation.

Example

This is a JavaScript program that finds the element at a given index after multiple rotations -

function findElement(arr, rotations, index) {
   // Number of rotations modulo length of the array
   rotations = rotations % arr.length;
     
   // New index after rotations
   let newIndex = (arr.length + index - rotations) % arr.length;
    
   // Return element at new index
   return arr[newIndex];
}
let arr = [1, 2, 3, 4, 5];
let rotations = 2;
let index = 4;
console.log(findElement(arr, rotations, index)); // Output: 3

In this example, the result is 4, which is at index 3 after 2 spins.

illustrate

• The function findElement takes three parameters: arr, rotation and index. arr is the array of elements, rotations is the number of rotations to be performed on the array, and index is the index of the element to be found after the rotations.

• The first line of the function calculates the number of rotations modulo the length of the array. This is done because if the number of rotations is greater than the length of the array, then after some rotations the array will return to its original state. Therefore, we only need to perform a rotation equal to the length of the array.

• The next line calculates the new index of the element after performing the rotation. It does this by subtracting the number of rotations from the given index and adding the length of the array to the result. The final step is to take the result modulo the array length.

• Finally, the function returns the element at the new index.

• In the code below, we initialize the array arr, the number of rotations and the index index

• The last line of code calls the findElement function and prints the result to the console.

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