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First Repeating Element
Easy Accuracy: 48.62% Submissions: 16635 Points: 2

Given an array arr[] of size N, find the first repeating element. The element should occurs more than once and the index of its first occurrence should be the smallest.

 

Example 1:

Input:
N = 7
arr[] = {1, 5, 3, 4, 3, 5, 6}
Output: 2
Explanation: 
5 is appearing twice and 
its first appearence is at index 2 
which is less than 3 whose first 
occuring index is 3.


Example 2:

Input:
N = 4
arr[] = {1, 2, 3, 4}
Output: -1
Explanation: 
All elements appear only once so 
answer is -1.


Your Task:
You don't need to read input or print anything. Complete the function firstRepeated() which takes arr and N as input parameters and return the position of the first repeating element. If there is no such element, return -1.
The position you return should be according to 1-based indexing. 

 

Expected Time Complexity: O(NlogN)
Expected Auxilliary Space: O(N)

 

Constraints:
1 <= N <= 106
0 <= Ai<= 106

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First Repeating Element

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