LeetCode - Algorithms - 349. Intersection of Two Arrays

Problem

349. Intersection of Two Arrays

Java

brute force method

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class Solution {
    public int[] intersection(int[] nums1, int[] nums2) {
        final int len1 = nums1.length;
        final int len2 = nums2.length;

        Set<Integer> ret = new HashSet<Integer>();
        for (int i = 0; i < len1; i++) {
            for (int j = 0; j < len2; j++) {
                if (nums1[i] == nums2[j])
                    ret.add(nums1[i]);
            }
        }
        int[] r = new int[ret.size()];
        int k = 0;
        for (Integer e : ret)
            r[k++] = e.intValue();
        return r;        
    }
}

Submission Detail

  • 60 / 60 test cases passed.
  • Runtime: 8 ms, faster than 11.36% of Java online submissions for Intersection of Two Arrays.
  • Memory Usage: 39.9 MB, less than 54.69% of Java online submissions for Intersection of Two Arrays.

retainAll of HashSet in Java collections framework

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class Solution {
    public int[] intersection(int[] nums1, int[] nums2) {
        Set<Integer> set1 = new HashSet<Integer>();
        Set<Integer> set2 = new HashSet<Integer>();
        for (int i = 0; i < nums1.length; i++)
            set1.add(nums1[i]);
        for (int i = 0; i < nums2.length; i++)
            set2.add(nums2[i]);
        set1.retainAll(set2);
        int[] r = new int[set1.size()];
        int k = 0;
        for (Integer e : set1)
            r[k++] = e.intValue();
        return r;        
    }
}

Submission Detail

  • 60 / 60 test cases passed.
  • Runtime: 2 ms, faster than 99.40% of Java online submissions for Intersection of Two Arrays.
  • Memory Usage: 39.4 MB, less than 90.00% of Java online submissions for Intersection of Two Arrays.