2766. Find the Prefix Common Array of Two Arrays
My accepted Python solution to LeetCode problem 2766, Find the Prefix Common Array of Two Arrays, running in 7ms.
- Difficulty: Medium
- Python
- Runtime 7ms
- Memory 17.3MB
- Updated
Read the problem on LeetCode View on GitHub
The problem statement is LeetCode’s and stays on their site. What follows is my accepted solution.
Python
Accepted on LeetCode — runtime 7ms, memory 17.3MB, accepted 2026-01-01.
class Solution:
def findThePrefixCommonArray(self, A: List[int], B: List[int]) -> List[int]:
n = len(A)
result = []
seen_a = set()
seen_b = set()
common = 0
for i in range(n):
seen_a.add(A[i])
seen_b.add(B[i])
# If A[i] was already in B, increment common
if A[i] in seen_b:
common += 1
# If B[i] was already in A (and B[i] != A[i]), increment common
if B[i] in seen_a and B[i] != A[i]:
common += 1
result.append(common)
return result