We have an integer array. For each integer, x, in the array, how many times does x + 1 appear? Count duplicates.
To easily solve this, we use a set() to conduct a lookup in O(1) time, placing all values of the input array into the set. Then, we just iterate through the entire list, checking each value, x. If x + 1 is in the set we created, we increase the count.
The solution is as follows:
class Solution:
def countElements(self, arr: List[int]) -> int:
set_arr = set(arr)
count = 0
for num in arr:
if num + 1 in set_arr:
count += 1
return count_ Time Complexity:
O(n) - We have to iterate through the entire input array.
_ Space Complexity:
O(n) - We have to create a set to store the input array.