Thanks for participation!
include<bits/stdc++.h>
using namespace std;
int main() { int tests; cin >> tests; while (tests--) { int n; cin >> n; vector a(n); for (auto& i : a) cin >> i; vector pos(n); iota(pos.begin(), pos.end(), 0); vector<pair<int, int>> ans; for (int i = n — 1; i; --i) { vector occ(i, -1); for (auto j : pos) { if (occ[a[j] % i] != -1) { ans.emplace_back(j, occ[a[j] % i]); pos.erase(find(pos.begin(), pos.end(), j)); break; } occ[a[j] % i] = j; } } reverse(ans.begin(), ans.end()); cout << "YES\n"; for (auto [x, y] : ans) cout << x + 1 << ' ' << y + 1 << '\n'; } } ~~~~~