Day 51.1.txt

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]
 

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




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