class Solution:
    def findThePrefixCommonArray(self, A: List[int], B: List[int]) -> List[int]:
        n = len(A)
        prefix_common_array = [0] * n
        frequency = [0 for _ in range(n + 1)]
        common_count = 0
        
        for current_index in range(n):
            frequency[A[current_index]] += 1
            if frequency[A[current_index]] == 2:
                common_count += 1
                
            frequency[B[current_index]] += 1
            if frequency[B[current_index]] == 2:
                common_count += 1
                
            prefix_common_array[current_index] = common_count
            
        return prefix_common_array