Algorithm

Problem Name: 349. Intersection of Two Arrays

Problem Link: https://leetcode.com/problems/intersection-of-two-arrays/
 

Given two integer arrays nums1 and nums2, return an array of their intersection. Each element in the result must be unique and you may return the result in any order.

 

Example 1:

Input: nums1 = [1,2,2,1], nums2 = [2,2]
Output: [2]

Example 2:

Input: nums1 = [4,9,5], nums2 = [9,4,9,8,4]
Output: [9,4]
Explanation: [4,9] is also accepted.

 

Constraints:

  • 1 <= nums1.length, nums2.length <= 1000
  • 0 <= nums1[i], nums2[i] <= 1000

Code Examples

#1 Code Example with C Programming

Code - C Programming


class Solution {
  public int[] intersection(int[] nums1, int[] nums2) {
    boolean[][] found = new boolean[1001][2];
    for (int num : nums1) {
      found[num][0] = true;
    }
    int count = 0;
    for (int num : nums2) {
      if (!found[num][1]) {
        if (found[num][0]) {
          count++;
        }
      }
      found[num][1] = true;
    }
    int[] result = new int[count];
    int idx = 0;
    for (int i = 1; i  < = 1000; i++) {
      if (found[i][0] && found[i][1]) {
        result[idx++] = i;
      }
    }
    return result;
  }
}
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Input

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nums1 = [1,2,2,1], nums2 = [2,2]

Output

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[2]

#2 Code Example with Javascript Programming

Code - Javascript Programming


const intersection = function(nums1, nums2) {
  const obj = {};
  nums1.forEach(i => (obj[i] = true));

  return nums2.filter(j => {
    if (obj[j]) {
      delete obj[j];
      return true;
    }
    return false;
  });
};
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Input

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nums1 = [1,2,2,1], nums2 = [2,2]

Output

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[2]

#3 Code Example with Python Programming

Code - Python Programming


class Solution:
    def intersection(self, nums1, nums2):
        """
        :type nums1: List[int]
        :type nums2: List[int]
        :rtype: List[int]
        """
        return list(set(nums1)&set(nums2))
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Input

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nums1 = [4,9,5], nums2 = [9,4,9,8,4]

Output

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[9,4]

#4 Code Example with C# Programming

Code - C# Programming


using System.Collections.Generic;

namespace LeetCode
{
    public class _0349_IntersectionOfTwoArrays
    {
        public int[] Intersection(int[] nums1, int[] nums2)
        {
            var set1 = new HashSet < int>(nums1);
            var set2 = new HashSet<int>(nums2);

            var result = new List < int>();
            foreach (var num in set1)
                if (set2.Contains(num)) result.Add(num);

            return result.ToArray();
        }
    }
}
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Input

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nums1 = [4,9,5], nums2 = [9,4,9,8,4]

Output

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[9,4]
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Demonstration

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