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First Repeating Element.cpp
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First Repeating Element.cpp
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//{ Driver Code Starts
// Initial template for C++
#include <bits/stdc++.h>
using namespace std;
// } Driver Code Ends
// User function template in C++
class Solution
{
public:
// Function to return the position of the first repeating element.
int firstRepeated(int arr[], int n)
{
unordered_map<int, int> mp;
for (int i = 0; i < n; i++)
{
mp[arr[i]]++; // storing the frequency of each element in map.
}
for (int i = 0; i < n; i++)
{
if (mp[arr[i]] > 1) // if frequency of current element in map is greater than 1, then we return the index.
{
return i + 1;
}
}
return -1;
}
};
//{ Driver Code Starts.
int main()
{
int t;
cin >> t;
while (t--)
{
int n;
cin >> n;
int arr[n];
for (int i = 0; i < n; ++i)
cin >> arr[i];
Solution ob;
cout << ob.firstRepeated(arr, n) << "\n";
}
return 0;
}
// } Driver Code Ends