1346. Check If N and Its Double Exist

Problem

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 (Java)

class Solution {
    public boolean checkIfExist(int[] arr) {
        for (int i = 0; i < arr.length; i++) {
            for (int j = 0; j < arr.length; j++) {
                if (i != j && (arr[i] * 2 == arr[j] || arr[i] == arr[j] * 2)) {
                    return true;
                }
            }
        }
        return false;
    }
}

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).