Number and its double in the given array.txt

Given an array arr of integers, check if there exists two integers N and M such that N is the double of M ( i.e. N = 2 * M).

More formally check if there exists two indices i and j such that :

i != j
0 <= i, j < arr.length
arr[i] == 2 * arr[j]
 

Example 1:

Input: arr = [10,2,5,3]
Output: true
Explanation: N = 10 is the double of M = 5,that is, 10 = 2 * 5.
Example 2:

Input: arr = [7,1,14,11]
Output: true
Explanation: N = 14 is the double of M = 7,that is, 14 = 2 * 7.
Example 3:

Input: arr = [3,1,7,11]
Output: false
Explanation: In this case does not exist N and M, such that N = 2 * M.
 

Constraints:

2 <= arr.length <= 500
-10^3 <= arr[i] <= 10^3




Solution:
class cp
{
public:
    
    bool check(vector <int> arr)
    {
        unordered_map <int, int> map;

        for(int i = 0 ; i < arr.size() ; i++)
        {
            if(map.find(arr[i] * 2) != map.end())
                return true;

            if(arr[i]%2 == 0 && map.find(arr[i]/2) != map.end())
                return true;

            map[arr[i]]++;
        }

        return false;
    }  

};


int main()
{
    cp c;

    int n;
    cin >> n;
    vector<int > arr;
    for(int i = 0 ; i < n; i++)
    {
        int x;
        cin >> x;
        arr.push_back(x);
    }

    cout << c.check(arr) << endl;

}