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c_cpp
a year ago
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#include <bits/stdc++.h> using namespace std; #define ll long long #define f(i, x, n) for (int (i) = x; (i) < (n); i++) int main() { int n; bool b = false; // freopen("input.txt", "r", stdin); // freopen("output.txt", "w", stdout); cin >> n; unordered_map<int, vector<int>> m; unordered_map<int, vector<int>>::iterator itr; f(i, 1, (2*n)+1) { int t; cin >> t; m[t].push_back(i); } for (auto itr = m.begin(); itr != m.end(); itr++) { if(itr->second.size() % 2 == 0) {b = true;} else { b = false; break; } } if(!b){cout << -1;} else { for (auto itr = m.begin(); itr != m.end(); itr++) { for(int i = 0; i < itr->second.size(); i += 2) {cout << itr->second[i] << " " << itr->second[i+1] << endl;} } } }
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