Single Element in a Sorted Array.py

class Solution:
    def singleNonDuplicate(self, nums: List[int]) -> int:
        return self.b_search(nums)[0]
    
    def b_search(self, nums):
        if len(nums) == 1:
            return nums
        mid = len(nums)//2
        a = nums[:mid]
        b = nums[mid:]
		
		# check if last & first element of the two sub lists are same
        if a[-1] == b[0]:
            a = a[:-1]
            b = b[1:]
		
		# ignore the sub list with even number of elements
        if len(a)%2:
            return self.b_search(a)
        else:
            return self.b_search(b)