JavaScript Program to Search a Target Value in a Rotated Array

In this article, we are going to implement a JavaScript program to Search for a target value in a rotated array.

Using Binary Search

In this approach, we begin by locating the middle element of the array. Next, we determine whether the target element is greater or smaller. If it’s greater, we proceed with the second half; otherwise, we focus on the first half.

Syntax:

while (left <= right) {
}

Example: Implementation of the above approach.

Javascript

const searchInRotatedArray =
    (inputArray,targetElement) => {
  let left = 0;
  let right = inputArray.length - 1;

  while (left <= right) {
      const mid = Math.floor(
          (left + right) / 2);
      if (inputArray[mid] === targetElement) {
          return mid}

      if (inputArray[left] <= inputArray[mid]) {
          if (targetElement >= inputArray[left] &&
              targetElement < inputArray[mid]) {
              right = mid - 1;}
          else {
              left = mid + 1}}
      else {
          if (
              targetElement > inputArray[mid] &&
              targetElement <= inputArray[right]) {
              left = mid + 1;}
          else {
              right = mid - 1}}}

// Target not found
  return -1;
};

const rotatedArray = [4, 5, 6, 7, 0, 1, 2,];
const targetElement = 1;
console.log(
    searchInRotatedArray(rotatedArray,targetElement));

Output

5

Using Linear Search

In this method, we iterate through the entire array using a loop. During each iteration, we verify if the current element matches the target element. If a match is found, we return the current iteration as the index.

Syntax:

if (arr[index] === targetElement) {
    return index;
}

Example: Implementation of the above appraoch.

Javascript

const searchInRotatedArray =
    (inputArray,targetElement) => {
  for (let index = 0;index < inputArray.length;index++) {
      if (inputArray[index] === targetElement) {
          return index}}

  // Target not found
  return -1;
};

const rotatedArray = [4, 5, 6, 7, 0, 1, 2];
const target = 0;
console.log(searchInRotatedArray(rotatedArray, target));

Output

4

Using Recursive Function

In this method, similar to binary search, we divide the array into two halves: the left half and the right half. We then apply a recursive binary search within these halves.

Syntax:

return searchInRotatedArray( nums, target, left, mid - 1) 

Example: Implementation of the above approach.

Javascript

const searchInRotatedArray =
    ( nums, target, left = 0, right = nums.length - 1) => {
  if (left > right) {

    // Target not found
    return -1}

  const mid = Math.floor(
    (left + right) / 2);
  if (nums[mid] === target) {
    return mid}

  if (nums[left] <= nums[mid]) {
    if (target >= nums[left] &&
      target < nums[mid]) {
      return searchInRotatedArray(
          nums , target , left , mid - 1 )}
    else {
      return searchInRotatedArray(
          nums, target, mid + 1, right)}}
  else {
    if (target > nums[mid] && target <= nums[right]) {
      return searchInRotatedArray(
          nums, target, mid + 1, right)}
    else {
      return searchInRotatedArray(
          nums, target, left, mid - 1)}}};

const rotatedArray = [5, 6, 7, 8, 9, 10, 1, 2, 3];
const target = 3;
console.log(searchInRotatedArray(rotatedArray,target));

Output

8