1346. Check If N and Its Double Exist

class Solution {
public:
    bool checkIfExist(vector<int>& arr) {
        int n = arr.size();
        bool cnt[2001] = {false}; // Boolean array to track whether a number has been seen

        for(int i = 0 ; i < n ; i++) {
            int x = arr[i] * 2 + 1000;
            if(x >= 0 && x <= 2000 && cnt[x]) //Check if 2 * arr[i] exists and not exceed the range
                return true; 
            x = arr[i] / 2 + 1000;
            if(arr[i] % 2 == 0 && cnt[x]) //ensure arr[i] is even and check if arr[i] / 2 exists
                return true; 
            cnt[arr[i] + 1000] = 1;
        }
        return false;
    }
};