singleelemnt.java

import java.util.*;
public class singleelemnt {
        public static int singleNonDuplicate(int[] nums) {
            int n = nums.length; // Size of the array.
    
            // Edge cases:
            if (n == 1)
            {
                return nums[0];
            }
            if (nums[0]!=nums[1])
            {
                return nums[0];
            }
            if (nums[n-1]!=nums[n-2])
                return nums[n-1];
    
            int low = 1, high = n - 2;
            while (low <= high) {
                int mid = (low + high) / 2;
    
                // If arr[mid] is the single element:
                if (nums[mid]!=nums[mid-1] && nums[mid] != nums[mid+1])
                {
                    return nums[mid];
                }
                if ((mid % 2 == 1 && nums[mid] == nums[mid - 1])
                    || (mid % 2 == 0 && nums[mid] == nums[mid + 1])) {
                //eliminate the left half:
                low = mid + 1;
            }
            //we are in the right:
            else {
                //eliminate the right half:
                high = mid - 1;
            }
        }
        return -1;
    }
    public static void main(String[] args) 
    {
        int[] arr = {1, 1, 2, 2, 3, 3, 4, 5, 5, 6, 6};
        System.out.println(singleNonDuplicate(arr));
    }
    }