human
I am working on the file "Python/leetcode/easy/strings-arrays.ipynb".
The first task is:
Q.7. Given an integer array arr, count how many elements x there are, such that x + 1 is also in arr. If there're duplicates in arr, count them seperately.
Can you write Python code for it?
assistant
#Here is the Python code you requested.

class Solution(object):
    def countElements(self, arr: List[int]) -> int:
        """
        :type arr: List[int]
        :rtype: int
        
        Method: Build a dictionary of all numbers in the list and then separately
                verify if (n+1) number exists in the dictionary for every n.
        """
        nums = {}
        for n in arr:
            if n not in nums:
                nums[n] = 1
        
        cnt = 0
        for n in arr:
            if n+1 in nums:
                cnt += 1
        
        return cnt

print(Solution().countElements([1,3,2,3,5,0]))

        if root.left is None and root.right is None:
            return 0
        
        def get_longest_path(root):
            if root.left is None and root.right is None:
                return 0
            elif root.left is None:
                return 1 + get_longest_path(root.right)
            elif root.right is None:
                return 1 + get_longest_path(root.left)
            else:
                return max(1 + get_longest_path(root.left), 1 + get_longest_path(root.right))
        
        return get_longest_path(root.left) + get_longest_path(root.right)