Task: Find the first repeating element in given an array of N elements. If it is present then print that index else print -1. Example: Input: 1 1 2 2 3 1 Output: 1 Here is the Code: Program in C++: #include<iostream> #include<bits/stdc++.h> using namespace std; int main() { int t; cin>>t; while(t--) { int n; cin>>n; int a[n]; unordered_map<int, int> m; for(int i=0;i<n;i++) { cin>>a[i]; m[a[i]]++; } int c=0; for(int i=0;i<n;i++) { if(m[a[i]]>1) { cout<<i+1<<endl; c=1; break; } } if(c==0) cout<<-1<<endl; } return 0; } Here is the Video: