- Difficulty: Medium
- Tags: LeetCode, Medium, Bit Manipulation, Array, Hash Table, leetcode-2657, O(n), Freq Table
Problem
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.
Example 2:
Input: A = [2,3,1], B = [3,1,2] Output: [0,1,3] Explanation: At i = 0: no number is common, so C[0] = 0. At i = 1: only 3 is common in A and B, so C[1] = 1. At i = 2: 1, 2, and 3 are common in A and B, so C[2] = 3.
Constraints:
1 <= A.length == B.length == n <= 50
1 <= A[i], B[i] <= n
It is guaranteed that A and B are both a permutation of n integers.