search_in_sorted_rotated_array.java

/*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
  */


public class searchInRotatedArray {

    //Brute force solution 
    
        public static int searchTarget(int nums[] , int target)
        {
            int result = -1;
            for(int i=0 ; i<nums.length ; i++)
            {
               if(nums[i]==target)
               {
                result = i;
               } 
            }
            return result ;
        }
    
    // Optimized Solution
    public static int search(int nums[], int l, int h, int target)
    {
        // l: The starting index
        // h: The ending index, you have to search the key in this range
        
        int start = 0;
        int end = nums.length-1;
        int result = -1;
        
        while(start <=end)
        {
        int mid = start +(end -start)/2;
        
        if(nums[mid]==target)
        {
            result = mid;
        } 
        
        
        if(nums[start]<=nums[mid])
        {
       if(nums[start]<=target && nums[mid]>=target)
        {
            end = mid-1;
        }
        
        else
        {
            start =mid+1;
        }
        }
        
        
       else
       {
       if(nums[mid]<=target && target<nums[end])
        {
          start=  mid+1;
        }
        else 
        {
            end = mid-1;
        }
        }
        }
        return result;
    }
   
    public static void main(String[] args)
    {
        int[] nums = {4,5,6,7,0,1,2};
        int target = 0;
        System.out.println(search(nums , 0 , 7 , target));
    }
}