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Problem of the day

You are given an array of integers 'ARR' containing N elements. Each integer is in the range [1, N-1], with exactly one element repeated in the array.

Your task is to find the duplicate element. The duplicate element may be repeated more than twice in the error, but there will be exactly one element that is repeated in the array.

Note :

```
All the integers in the array appear only once except for precisely one integer which appears two or more times.
```

Detailed explanation

Input format:

```
The first line of input contains an integer ‘T’ denoting the number of test cases. Then the T test cases follow.
The first line of each test case contains an integer ‘N’, the number of elements in the array.
The second line of each test case contains ‘N’ space-separated integers representing the elements of the array.
```

Output format:

```
For each test case, the duplicate element of the given array is printed.
The output of each test case is printed in a separate line.
```

```
1 <= T <= 5
1 <= N <= 10^5
1 <= ARR[i] <= N - 1
Time Limit: 1 sec
```

```
1
3
1 1 2
```

```
1
```

```
1 is repeated in the array, hence function returns 1.
```

```
3
5
1 3 4 2 2
5
3 1 3 4 2
3
1 1 1
```

```
2
3
1
```