Intersection of Two Arrays Using Hash Map

function intersection(nums1, nums2) {
  const set1 = new Set(nums1);
  const res = new Set();
  for (let num of nums2) if (set1.has(num)) res.add(num);
  return Array.from(res);
}
                  

Explanation: Convert one array to a set and check each element of the second array for existence. This ensures unique intersections.

⏱ O(n + m) | 💾 O(n + m)

class Solution {
  public int[] intersection(int[] nums1, int[] nums2) {
    Set<Integer> set1 = new HashSet<>();
    for(int n:nums1) set1.add(n);
    Set<Integer> res = new HashSet<>();
    for(int n:nums2) if(set1.contains(n)) res.add(n);
    int[] ans = new int[res.size()];
    int i=0; for(int n:res) ans[i++]=n;
    return ans;
  }
}
                  

Explanation: HashSet ensures constant time lookup and uniqueness of intersection elements.

⏱ O(n + m) | 💾 O(n + m)

def intersection(nums1, nums2):
    set1 = set(nums1)
    return list({num for num in nums2 if num in set1})
                  

Explanation: Use set to check membership and return unique intersection elements.

⏱ O(n + m) | 💾 O(n + m)