search-in-rotated-sorted-array.js

/**
 * Search in Rotated Sorted Array
 *
 * 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.
 */

/**
 * @param {number[]} nums
 * @param {number} target
 * @return {number}
 */
const search = (nums, target) => {
  if (nums.length === 0) {
    return -1;
  }

  let lo = 0;
  let hi = nums.length - 1;

  while (lo <= hi) {
    const mid = lo + Math.floor((hi - lo) / 2);

    if (nums[mid] === target) {
      return mid;
    }

    // use <= here because lo might be equal to mid due to
    // mid = (lo + hi) / 2
    if (nums[lo] <= nums[mid]) {
      if (nums[lo] <= target && target < nums[mid]) {
        hi = mid - 1;
      } else {
        lo = mid + 1;
      }
    } else {
      if (nums[mid] < target && target <= nums[hi]) {
        lo = mid + 1;
      } else {
        hi = mid - 1;
      }
    }
  }

  return -1;
};

export default search;