| #include <bits/stdc++.h> |
| using namespace std; |
|
|
| int main() { |
| ios::sync_with_stdio(false); |
| cin.tie(nullptr); |
| |
| int T; |
| if (!(cin >> T)) return 0; |
| while (T--) { |
| int n; |
| cin >> n; |
| vector<string> s(n); |
| for (int i = 0; i < n; ++i) cin >> s[i]; |
|
|
| bool ok = true; |
| for (int i = 0; i < n && ok; ++i) { |
| if (s[i][i] != '1') ok = false; |
| for (int j = i + 1; j < n; ++j) |
| if (s[i][j] == '1' && s[j][i] == '1') ok = false; |
| } |
| if (!ok) { |
| cout << "No\n"; |
| continue; |
| } |
|
|
| |
| vector<vector<int>> desc(n); |
| vector<int> cnt(n); |
| for (int i = 0; i < n; ++i) { |
| int c = 0; |
| for (int j = 0; j < n; ++j) |
| if (s[i][j] == '1') ++c; |
| cnt[i] = c; |
| } |
| for (int i = 0; i < n; ++i) desc[i].reserve(cnt[i]); |
| for (int i = 0; i < n; ++i) |
| for (int j = 0; j < n; ++j) |
| if (s[i][j] == '1') desc[i].push_back(j); |
|
|
| |
| vector<int> order(n); |
| iota(order.begin(), order.end(), 0); |
| sort(order.begin(), order.end(), |
| [&](int a, int b) { return cnt[a] > cnt[b]; }); |
|
|
| vector<int> seen(n, 0); |
| vector<pair<int,int>> edges; |
| edges.reserve(n - 1); |
|
|
| for (int i = 0; i < n && (int)edges.size() < n; ++i) { |
| int cur = i + 1; |
| seen[i] = cur; |
| for (int v : order) { |
| if (s[i][v] != '1' || seen[v] == cur) continue; |
| edges.emplace_back(i, v); |
| if ((int)edges.size() >= n) break; |
| for (int w : desc[v]) seen[w] = cur; |
| } |
| } |
|
|
| if ((int)edges.size() != n - 1) { |
| cout << "No\n"; |
| continue; |
| } |
|
|
| vector<vector<int>> out(n), und(n); |
| for (auto [x, y] : edges) { |
| out[x].push_back(y); |
| und[x].push_back(y); |
| und[y].push_back(x); |
| } |
|
|
| |
| vector<char> vis(n, 0); |
| vector<int> st; |
| st.reserve(n); |
| st.push_back(0); |
| vis[0] = 1; |
| int visited = 0; |
| while (!st.empty()) { |
| int u = st.back(); st.pop_back(); |
| ++visited; |
| for (int w : und[u]) |
| if (!vis[w]) { |
| vis[w] = 1; |
| st.push_back(w); |
| } |
| } |
| if (visited != n) { |
| cout << "No\n"; |
| continue; |
| } |
|
|
| |
| vector<char> reach(n); |
| for (int u = 0; u < n && ok; ++u) { |
| fill(reach.begin(), reach.end(), 0); |
| vector<int> stack; |
| stack.reserve(n); |
| stack.push_back(u); |
| reach[u] = 1; |
| while (!stack.empty()) { |
| int x = stack.back(); stack.pop_back(); |
| for (int y : out[x]) |
| if (!reach[y]) { |
| reach[y] = 1; |
| stack.push_back(y); |
| } |
| } |
| for (int v = 0; v < n; ++v) |
| if ((s[u][v] == '1') != reach[v]) { |
| ok = false; |
| break; |
| } |
| } |
|
|
| if (!ok) { |
| cout << "No\n"; |
| continue; |
| } |
|
|
| cout << "Yes\n"; |
| for (auto [x, y] : edges) |
| cout << x + 1 << ' ' << y + 1 << '\n'; |
| } |
| return 0; |
| } |
