Find the Difference of Two Arrays

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

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

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

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

 

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] = [].

Approach

Java

import java.util.ArrayList;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;

public class DiffTwoArray {
    public static void main(String[] args) {

        int nums1[] = { 1, 2, 3 }, nums2[] = { 2, 4, 6 };

        System.out.println(findDifference(nums1, nums2));

    }

    public static List<List<Integer>> findDifference(int[] nums1, int[] nums2) {

        // creating the sets
        Set<Integer> st1 = new HashSet<Integer>();
        Set<Integer> st2 = new HashSet<Integer>();

        // add all the elements of first arrays into the set 1
        for (int i = 0; i < nums1.length; i++) {
            st1.add(nums1[i]);
        }

        // add all the elements of second arrays into the set 2
        for (int i = 0; i < nums2.length; i++) {
            st2.add(nums2[i]);
        }

        // remove the element which present in the set 1 and from array 2
        for (int i = 0; i < nums2.length; i++) {
            if (st1.contains(nums2[i]))
                st1.remove(nums2[i]);
        }

        // remove the element which present in the set 2 and from array 1
        for (int i = 0; i < nums1.length; i++) {
            if (st2.contains(nums1[i]))
                st2.remove(nums1[i]);
        }

        // creating the lists
        List<Integer> answer1 = new ArrayList<Integer>();

        List<Integer> answer2 = new ArrayList<Integer>();

        Iterator<Integer> value1 = st1.iterator();
        // add the set 1 element into list 1
        while (value1.hasNext()) {
            answer1.add(value1.next());
        }

        Iterator<Integer> value2 = st2.iterator();

        // add the set 1 element into list 1
        while (value2.hasNext()) {
            answer2.add(value2.next());
        }

        List<List<Integer>> result = new ArrayList<List<Integer>>();

        // add both the list into one list
        result.add(answer1);
        result.add(answer2);

        // return the final list
        return result;

    }
}

C++

#include <bits/stdc++.h>
using namespace std;

vector<vector<int>> findDifference(vector<int> &nums1, vector<int> &nums2)
{
    set<int> st1, st2;

    // insert the first array elements into set 1
    for (int i = 0; i < nums1.size(); i++)
    {

        st1.insert(nums1[i]);
    }

    // insert the second array elements into set 2
    for (int i = 0; i < nums2.size(); i++)
    {
        st2.insert(nums2[i]);
    }

    // remove the element from set 1 which present in second array
    for (int i = 0; i < nums2.size(); i++)
    {
        if (st1.find(nums2[i]) != st1.end())
            st1.erase(nums2[i]);
    }

    // remove the element from set 2 which present in first array
    for (int i = 0; i < nums1.size(); i++)
    {
        if (st2.find(nums1[i]) != st2.end())
            st2.erase(nums1[i]);
    }

    vector<int> answer1, answer2;
    for (auto it = st1.begin(); it != st1.end(); ++it)
    {
        answer1.push_back(*it);
    }

    for (auto it = st2.begin(); it != st2.end(); ++it)
    {
        answer2.push_back(*it);
    }

    vector<vector<int>> result;
    result.push_back(answer1);
    result.push_back(answer2);

    return result;
}
int main()
{
    vector<int> nums1 = {1, 2, 3}, nums2 = {2, 4, 6};

    vector<vector<int>> result = findDifference(nums1, nums2);

    cout << "[";
    for (int i = 0; i < result.size(); i++)
    {
        cout << "[";
        for (int j = 0; j < result[i].size(); j++)
        {
            cout << result[i][j];
            if (j != result[i].size() - 1)
                cout << ",";
        }
        cout << "]";
        if (i != result.size() - 1)
            cout << ",";
    }
    cout << "]";
}

Output:

[[1, 3], [4, 6]]