1468. Check If N And Its Double Exist¶

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1468. Check If N and Its Double Exist

Easy

Given an array arr of integers, check if there exist 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: For i = 0 and j = 2, arr[i] == 10 == 2 * 5 == 2 * arr[j]

Example 2:

Input: arr = [3,1,7,11]
Output: false
Explanation: There is no i and j that satisfy the conditions.

Constraints:

• 2 <= arr.length <= 500
• -103 <= arr[i] <= 103

Solution¶

class Solution {
    public boolean checkIfExist(int[] arr) {
        int n = arr.length;
        HashMap<Integer, Integer> map = new HashMap<>();
        for (int i = 0; i < n; i++) {
            int current = arr[i];
            if (map.containsKey(current * 2)) return true;
            if (current % 2 == 0 && map.containsKey(current / 2)) return true;
            map.put(current, i);
        }
        return false;
    }
}

Complexity Analysis¶

• Time Complexity: O(?)
• Space Complexity: O(?)

Approach¶

Detailed explanation of the approach will be added here