X. Counting Elements

Easy

Given an integer array arr, count element x such that x + 1 is also in arr. If there're duplicates in arr, count them separately.

😇 Solution

O(n2)

class Solution:
    def countElements(self, arr: List[int]) -> int:
        
        count = 0
        
        for a in arr:
            if a+1 in arr:
                count += 1
                
        return count