Given an integer array arr, determine whether there exist two distinct indices i and j such that arr[i] is exactly double arr[j]. Return true if such a pair exists, otherwise return false.

Note: The indices i and j must be different.

Constraints:

• $2 \leq$ arr.length $\leq 500$

• $-10^3 \leq$ arr[i] $\leq 10^3$

Input: arr = [4, 9, 2, 18]-List[int]
Output: true-bool
Explanation: 4 is double 2 (4 = 2 * 2), and they are at different indices.

Input: arr = [-6, 0, 3, 12]-List[int]
Output: false-bool
Explanation: Although 12 is double 6, the array contains -6 (not 6). Also, 0 would require another 0 to form a valid pair, but there is only one 0.

Input: arr = [1, 5, 7, 13, 19]-List[int]
Output: false-bool
Explanation: No element in the array is exactly double another element.

Input: arr = [0, 0]-List[int]
Output: true-bool
Explanation: 0 is double 0 (0 = 2 * 0), and there are two distinct indices containing 0.

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