[LeetCode] 349. Intersection of Two Arrays

Given two arrays, write a function to compute their intersection.
Example:
Given nums1 = [1, 2, 2, 1], nums2 = [2, 2], return [2].
Note:
  • Each element in the result must be unique.
  • The result can be in any order.

Thought process:
Iterate through nums1. Put the elements into a hash set. Iterate through nums2. The elements that the hash set contains are the intersection.

Solution:

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class Solution {
    public int[] intersection(int[] nums1, int[] nums2) {
        Set<Integer> set = new HashSet<>();
        for (int num : nums1) {
            set.add(num);
        }
        
        Set<Integer> intersection = new HashSet<>();
        for (int num : nums2) {
            if (set.contains(num)) {
                intersection.add(num);
            }
        }
        
        int[] array = new int[intersection.size()];
        int i = 0;
        for (int num : intersection) {
            array[i] = num;
            i++;
        }
        return array;
    }
}

Time complexity: O(a + b).
Location: Philadelphia, PA, USA

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