14_findThePrefixCommonArray.py

''' Time Complexity O(N)
You are given two 0-indexed integer permutations A and B of length n.
A prefix common array of A and B is an array C such that C[i] is equal to the count of numbers
that are present at or before the index i in both A and B.
Return the prefix common array of A and B.
A sequence of n integers is called a permutation if it contains all integers from 1 to n exactly once.
Example 1:

Input: A = [1,3,2,4], B = [3,1,2,4]
Output: [0,2,3,4]
Explanation: At i = 0: no number is common, so C[0] = 0.
At i = 1: 1 and 3 are common in A and B, so C[1] = 2.
At i = 2: 1, 2, and 3 are common in A and B, so C[2] = 3.
At i = 3: 1, 2, 3, and 4 are common in A and B, so C[3] = 4.'''
from typing import List
class Solution:
    def findThePrefixCommonArray(self, A: List[int], B: List[int]) -> List[int]:
        size=len(A)+1
        count=[0]*size
        ans=[]
        preFix=0
        for i,j in zip(A,B):
            count[i]+=1
            if count[i]==2:preFix+=1
            count[j]+=1
            if count[j]==2:preFix+=1
            ans.append(preFix)
        return ans