package LeetCode_33 /** * 33. Search in Rotated Sorted Array * https://leetcode.com/problems/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 * */ class Solution { fun search(nums: IntArray, target: Int): Int { //try to find the pivot point,then divide a array into two sub-arrays and call binary search return searchHelp(nums, target, 0, nums.size - 1) } private fun searchHelp(nums: IntArray, target: Int, left: Int, right: Int): Int { if (left > right) { return -1 } val mid = (left + right) / 2 if (nums[mid] == target) { return mid } //if num[left..mid] first subarray is sorted if (nums[left] <= nums[mid]) { if (target >= nums[left] && target <= nums[mid]) { return searchHelp(nums, target, left, mid - 1) } return searchHelp(nums, target, mid + 1, right) } //if num[left..mid] first subarray is not sorted, num[mid+1,right] must be sorted if (target >= nums[mid] && target <= nums[right]) { return searchHelp(nums, target, mid + 1, right) } return searchHelp(nums, target, left, mid - 1) } }