Search in Rotated Sorted Array

Description

Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand.

(i.e., [0,1,2,4,5,6,7] might become [4,5,6,7,0,1,2]).

You are given a target value to search. If found in the array return its index, otherwise return -1.

You may assume no duplicate exists in the array.

Your algorithm's runtime complexity must be in the order of O(log n).

Example 1:

Input: nums = [4,5,6,7,0,1,2], target = 0
Output: 4

Example 2:

Input: nums = [4,5,6,7,0,1,2], target = 3
Output: -1

Solution(javascript)

/**
 * @param {number[]} nums
 * @param {number} target
 * @return {number}
 */
var search = function(nums, target) {
  let left = 0;
  let right = nums.length - 1;
    
  while (left <= right) {
    let mid = Math.floor((left + right) / 2);
    
    if (nums[mid] === target) {
      return mid;
    }
    
    // When dividing the roated array into two halves, one must be sorted.
    
    // Check if the left side is sorted
    if (nums[left] <= nums[mid]) {
      if (nums[left] <= target && target <= nums[mid]) {
        // target is in the left
        right = mid - 1;
        
      } else {
        // target is in the right
        left = mid + 1;
      }
    } 
    
    // Otherwise, the right side is sorted
    else {
      if (nums[mid] <= target && target <= nums[right]) {
        // target is in the right
        left = mid + 1;

      } else {
        // target is in the left
        right = mid - 1;
      }
    }
    
    
  }
    
  return -1;
};