题目
Given an integer array arr, count element x such that x + 1 is also in arr.
If there’re duplicates in arr, count them seperately.
解题思路
将数组转换成set，遍历set中的每个元素x，检查x+1是否出现在set中
代码
class Solution:
def countElements(self, arr: List[int]) -> int:
return len([0 for x in arr if (x + 1) in set(arr)])
