# Two Non-Repeating Elements

Posted: 15 Sep, 2020
Difficulty: Moderate

## PROBLEM STATEMENT

#### Given an array 'ARR' of integers of size N in which two elements appear exactly once and all other elements appear exactly twice. Your task is to find the two elements that appear only once.

##### Note
`````` 1. Input will always have only two integers that appear exactly once rest will appear twice.
2. Try to do this in linear time and constant space.
``````
##### Input Format:
``````The first line of input contains an integer N representing the size of the array.

The second line of input contains an N space-separated integers representing the array elements.
``````
##### Output Format:
``````Print the two space-separated elements that appear only once where the first integer is less than the second integer.
``````
##### Constraints:
``````2 <= N <= 10^5
-10^5 <= ARR[i] <= 10^5

Time Limit: 1 sec
`````` Approach 1
• We will maintain a list or vector to store the two elements that appear only once.
• We will run a loop from i = 0 to i = N - 1 and for i’th loop, we need to check if there is another element with the same value is present or not so we will run another loop from j = 0 j = N - 1 and if i is not equal to j check if ARR[i] is equal to ARR[j]. If it is equal for any j that means i’th element is repeated otherwise add the i’th element to the list.
• Now print the answer as mentioned in the problem statement.