• 33. Search in Rotated Sorted Array


    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)
        }
    }
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  • 原文地址:https://www.cnblogs.com/johnnyzhao/p/12883039.html
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