Find the first non-repeating element in a given array** A** of **N** integers.

**Note:** Array consists of only positive and negative integers and **not zero**.

**Input:**

The first line of input is an integer** T**, denoting the number of test cases. Each test case has subsequent two lines of input. First line is an integer **N**, denoting size of integer array **A**. Second line consists of **N** space separated integers of the array **A**.

**Output:**

For each testcase, print the required answer. If no such element exists, then print **0**

**Constraints:**

1 <= T <= 100;

1 <= N <= 10^{7};

-10^{16} <= A_{i }<= 10^{16}

{A_{i} !=0 }

**Example:
Input:**

4

5

-1 2 -1 3 2

6

9 4 9 6 7 4

3

1 1 1

2

-3 2

3

6

0

-3

**Explanation:**

**Testcase1: **-1 and 2 are repeating whereas 3 is the only number occuring once. Hence, the output is 3.

**Testcase2:** There are 3 distinct integers, 9, 4 and 5, but they all are repeating. There is no non-repetitive element in the array. Hence, the output is **0**.

**Testcase3:** -1 and 3 are non-repeating. -1 occurs before 3 in the array. Hence, the output is -1.

**Testcase4:** There are two distinct elements occuring only once in the array, with 6 occuring before 7. Hence, output is 6.

**Testcase5:** The only non-repeating element is -3. Hence, output is -3.

If you have purchased any course from GeeksforGeeks then please ask your doubt on course discussion forum. You will get quick replies from GFG Moderators there.

jhasaurabh312 | 138 |

Aaaaarohiiii | 136 |

Harsha_kunchala | 128 |

tushki | 124 |

RajaRajput | 117 |

ARUN_PUNDIR | 617 |

manishgupta8497 | 607 |

Abhimanyu_kumar | 559 |

KhyatiSoneji | 501 |

Aman___Jain | 496 |

blackshadows | 5335 |

Ibrahim Nash | 5223 |

akhayrutdinov | 5111 |

mb1973 | 4929 |

Quandray | 4567 |

Login to report an issue on this page.