1346 - Check if N and its Double Exist

1346 - Check if N and its Double Exist

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]

Examples

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

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

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

Java Solution

class Solution {
    public boolean checkIfExist(int[] arr) {
        Set<Integer> set = new HashSet();
        for (int n : arr) {
            if (set.contains(2*n) || (n%2 == 0 && set.contains(n/2)))
                return true;
            set.add(n);
        }
        return false;
    }
}