33. Search in Rotated Sorted Array

Problem Statement

There is an integer array nums sorted in ascending order (with distinct values).

Prior to being passed to your function, nums is possibly rotated at an unknown pivot index k (1 <= k < nums.length) such that the resulting array is [nums[k], nums[k+1], ..., nums[n-1], nums[0], nums[1], ..., nums[k-1]] (0-indexed). For example, [0,1,2,4,5,6,7] might be rotated at pivot index 3 and become [4,5,6,7,0,1,2].

Given the array nums after the possible rotation and an integer target, return the index of target if it is in nums, or -1 if it is not in nums.

You must write an algorithm with O(log n) runtime complexity.

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

Example 3:

Input: nums = [1], target = 0
Output: -1

Constraints:

1 <= nums.length <= 5000
-104 <= nums[i] <= 104
All values of nums are unique.
nums is an ascending array that is possibly rotated.
-104 <= target <= 104

Intuition

Approach:

Take the help of first and last element to judge the poistion of the target
element

Links

https://leetcode.com/problems/search-in-rotated-sorted-array/description/

Video Links

Approach 1:

C++

class Solution {
public:
    int search(vector<int>& nums, int target) {
        int low=0, high=nums.size()-1;
        while(low<=high){
            int mid = low+(high-low)/2;
            if(nums[mid] == target)
                return mid;
            else if(nums[low] <= nums[mid]){
                if(nums[low] <= target and target <= nums[mid])
                    high = mid-1;
                else
                    low = mid+1;
            }
            else{
                if(nums[mid] <= target and target <= nums[high])
                    low = mid+1;
                else
                    high = mid-1;
            }
        }

        return -1;
    }
};

Approach 2:

C++

Approach 3:

C++

Approach 4:

C++