2215.Find the Difference of Two Arrays
===

###### tags: `Easy`,`Array`,`Hash Table`

[2215. Find the Difference of Two Arrays](https://leetcode.com/problems/find-the-difference-of-two-arrays/)

### 題目描述

Given two **0-indexed** integer arrays `nums1` and `nums2`, return *a list* `answer` *of size* `2` *where:*

* `answer[0]` *is a list of all **distinct** integers in* `nums1` *which are **not** present in* `nums2`.
* `answer[1]` *is a list of all **distinct** integers in* `nums2` *which are **not** present in* `nums1`.

**Note** that the integers in the lists may be returned in **any** order.

### 範例

**Example 1:**

Input: nums1 = [1,2,3], nums2 = [2,4,6]
Output: [[1,3],[4,6]]
Explanation:
For nums1, nums1[1] = 2 is present at index 0 of nums2, whereas nums1[0] = 1 and nums1[2] = 3 are not present in nums2. Therefore, answer[0] = [1,3].
For nums2, nums2[0] = 2 is present at index 1 of nums1, whereas nums2[1] = 4 and nums2[2] = 6 are not present in nums2. Therefore, answer[1] = [4,6].

**Example 2:**

Input: nums1 = [1,2,3,3], nums2 = [1,1,2,2]
Output: [[3],[]]
Explanation:
For nums1, nums1[2] and nums1[3] are not present in nums2. Since nums1[2] == nums1[3], their value is only included once and answer[0] = [3].
Every integer in nums2 is present in nums1. Therefore, answer[1] = [].

**Constraints**:

* 1 <= `nums1.length`, `nums2.length` <= 1000
* -1000 <= `nums1[i]`, `nums2[i]` <= 1000

### 解答

#### TypeScript

function findDifference(nums1: number[], nums2: number[]): number[][] {
  const set1 = new Set(nums1);
  const set2 = new Set(nums2);

  set1.forEach((item) => {
    if (set2.has(item)) {
      set2.delete(item);
      set1.delete(item);
    }
  });

  return [[...set1], [...set2]];
}

> [name=Sheep][time=Wed, May 3, 2023]

#### Javascript

function findDifference(nums1, nums2) {
  const set1 = new Set(nums1);
  const set2 = new Set(nums2);

  for (const item of set1) {
    if (set2.has(item)) {
      set1.delete(item);
      set2.delete(item);
    }
  }

  return [[...set1], [...set2]];
}

> 慚愧，跟我弟學習了，本來用set1去刪set2然後再用set2刪set1，不止要做兩遍還要多建一個set根本87
> [name=Marsgoat][time=Wed, May 3, 2023]

#### Python

class Solution:
    def findDifference(self, nums1: List[int], nums2: List[int]) -> List[List[int]]:
        return [list(set(nums1) - set(nums2)), list(set(nums2) - set(nums1))]

> [name=Ron Chen][time=Wed, May 3, 2023]

#### C#

public IList<IList<int>> FindDifference(int[] nums1, int[] nums2) {
    HashSet<int> set1 = new HashSet<int>(nums1);
    HashSet<int> set2 = new HashSet<int>(nums2);

    foreach(int num in set2) {
        if (set1.Contains(num)) {
            set1.Remove(num);
            set2.Remove(num);
        }
    }
    
    return new List<IList<int>>(){ set1.ToList(), set2.ToList()};
}

> [name=Jim][time=Wed, May 3, 2023]

#### Java

class Solution {
    public List<List<Integer>> findDifference(int[] nums1, int[] nums2) {
        Set<Integer> set1 = new HashSet<>();
        Set<Integer> set2 = new HashSet<>();

        for(Integer num : nums1) {
            set1.add(num);
        }

        for(Integer num : nums2) {
            set2.add(num);
        }

        Set<Integer> difference1 = new HashSet<>(set1);
        difference1.removeAll(set2);
        Set<Integer> difference2 = new HashSet<>(set2);
        difference2.removeAll(set1);

        List<List<Integer>> ans = new ArrayList<>();
        ans.add(difference1.stream().toList());
        ans.add(difference2.stream().toList());

        return ans;
    }
}

> 只能醜醜寫的我
> [name=Ron Chen][time=Wed, May 3, 2023]

class Solution {
    public List<List<Integer>> findDifference(int[] nums1, int[] nums2) {
        Set<Integer> set1 = Arrays.stream(nums1).boxed().collect(Collectors.toSet());

        // Delete nums2 element which in set1 and assign to set2
        Set<Integer> set2 = Arrays.stream(nums2).filter(n -> !set1.contains(n)).boxed().collect(Collectors.toSet());

        // Delete set1 element which in nums2
        Arrays.stream(nums2).forEach(set1::remove);

        return Arrays.asList(new ArrayList<>(set1), new ArrayList<>(set2));
    }
}

> 解答區看到的 Java Stream API 用法，太猛了

### Reference

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