Find The Single Element

Easy

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Average time to solve is 10m

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Problem statement

You are given a sorted array 'arr' of positive integers of size 'n'.

It contains each number exactly twice except for one number, which occurs exactly once.

Find the number that occurs exactly once.

Example :

Input: ‘arr’ = {1, 1, 2, 3, 3, 4, 4}.

Output: 2

Explanation: 1, 3, and 4 occur exactly twice. 2 occurs exactly once. Hence the answer is 2.

Detailed explanation ( Input/output format, Notes, Images )

Input format:

The first line contains an integer ‘n’, representing the size of the array ‘arr’.

The second line contains ‘n’ integers, denoting the elements of the array ‘arr’.

Output Format:

The output contains the integer in the array that occurs exactly once.

Note :

You do not need to print anything; it has already been taken care of. Just implement the given function.

Sample Input 1:

5
1 1 2 2 3

Sample Output 1:

Explanation of sample output 1:

{1, 2} each occurs twice, whereas 3 occurs only once.
Hence the answer is 3.

Sample Input 2:

5
8 8 9 9 10

Sample Output 2:

Expected time complexity :

The expected time complexity is O(n), but try solving it in O(log n).

Constraints:

1 <= 'n' <= 10^4
1 <= 'arr[i]' <= 10^9

‘n’ is always odd.

Time Limit: 1 sec

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