Given an array arr of size N, the goal is to find out the smallest number that is repeated exactly ‘K’ times.

Example 1:
Input:
N=5, K=2
arr[] = { 2 2 1 3 1 }
Output: 1
Explanation: Here in array,
2 is repeated 2 times, 1 is repeated
2 times, 3 is repeated 1 time.
Hence 2 and 1 both are repeated 'k'
times i.e 2 and min(2, 1) is 1 .

Example 2:
Input:
N=4, K=1
arr[] = { 3 5 3 2 }
Output: 2
Explanation: Both 2 and 5 are repeating 1
time but min(5, 2) is 2.

Your Task:
You just need to complete the function findDuplicate() that takes array arr, integer N and integer K as parameters and returns the required answer.
Note- If there is no such element then return -1.

Expected Time Complexity: O(N)
Expected Auxiliary Space: O(MAX). where MAX is maximum element in the array.

Constraints:
1 ≤ N ≤ 10^{5}
1 ≤ arr[i] ≤ 10^{5}

见题面

见题面