2657. Find the Prefix Common Array of Two Arrays

Explanation:

To find the prefix common array of two arrays A and B, we iterate through both arrays simultaneously and count the numbers that are common up to the current index. We keep track of the count in a separate array C.

Initialize an array C of size n with all elements as 0.
Iterate through arrays A and B simultaneously.
For each index i, count the common elements up to index i in arrays A and B.
Update the count in array C at index i.
Return the array C as the prefix common array.

Time complexity: O(n) where n is the length of the input arrays A and B. Space complexity: O(n) for the output array C.

View Leetcode Problem

class Solution {
    public int[] prefixCommonArray(int[] A, int[] B) {
        int n = A.length;
        int[] C = new int[n];
        
        for (int i = 0; i < n; i++) {
            int count = 0;
            for (int j = 0; j <= i; j++) {
                if (contains(A, B, A[j])) {
                    count++;
                }
            }
            C[i] = count;
        }
        
        return C;
    }
    
    private boolean contains(int[] A, int[] B, int num) {
        for (int i = 0; i < A.length; i++) {
            if (A[i] == num && B[i] == num) {
                return true;
            }
        }
        return false;
    }
}

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