Why this is not O(N)


Someone please tell me why this solution is not O(N)
class Solution:
# @param A : list of integers
# @param B : integer
# @return an integer
def diffPossible(self, A, B):
if B==0:
for i in range(len(A)-1):
if A[i]==A[i+1]:
return 1
return 0
for i in range(len(A)):
if A[i]+B in A:
return 1
return 0


How do you think is this line getting evaluated internally?
if A[i]+B in A:
This line in itself is an O(N) operation and you are iterating over this N times.
Your algorithm thus is O(N^2)