Search in Rotated Sorted Array

Problem Statement - link #

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.

Examples #

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
• -10^4 <= nums[i] <= 10^4
• All values of nums are unique.
• nums is an ascending array that is possibly rotated.
• -10^4 <= target <= 10^4

Solutions #

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