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Check If N And Its Double Exist

Problem Description​

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​

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​

  • -103 <= arr[i] <= 103

Solution Approach​

Intuition:​

To efficiently determine the n and if it's double exists or not.

Solution Implementation​

Code (C++):​

class Solution {
public:
    bool checkIfExist(vector<int>& arr) {
        for(int i=0; i<arr.size(); i++){
            for(int j=0; j<arr.size(); j++){
               if(arr[i]==2*arr[j] && i!=j) return true;

            }
        }
        return false;
    }
};