[LeetCode][2215. Find the Difference of Two Arrays] Java HashSet Solution

By Long Luo

This article is the solution Java HashSet Solution of Problem 2215. Find the Difference of Two Arrays.

Intuition

We can use $\texttt{HashSet}$ to record the distinct integers of the two arrays and judge whether a distinct integer in $\textit{nums}_1$ which not present in $\textit{nums}_2$.

We can only use $2$ $\texttt{HashSet}$, not $4$ $\texttt{HashSet}$.

public List<List<Integer>> findDifference(int[] nums1, int[] nums2) {
    Set<Integer> set1 = new HashSet<>();
    Set<Integer> set2 = new HashSet<>();
    for (int num : nums1) {
        set1.add(num);
    }
    for (int num : nums2) {
        set2.add(num);
        set1.remove(num);
    }

    for (int num : nums1) {
        set2.remove(num);
    }

    List<List<Integer>> ans = new ArrayList<>();
    ans.add(new ArrayList<>(set1));
    ans.add(new ArrayList<>(set2));
    return ans;        
}

Analysis

• Time Complexity: $O(m+n)$.
• Space Complexity: $O(m+n)$.

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