Finding duplicate values between two arrays

Question

Let\'s say I have the following two arrays:

int[] a = [1,2,3,4,5];
int[] b = [8,1,3,9,4];

I would like to take the first value of array

Answer 1

These solutions all take O(n^2) time. You should leverage a hashmap/hashset for a substantially faster O(n) solution:

void findDupes(int[] a, int[] b) {
    HashSet map = new HashSet();
    for (int i : a)
        map.add(i);
    for (int i : b) {
        if (map.contains(i))
            // found duplicate!   
    }
}