#include using namespace std; // ---- Matrix generation ---- struct TestCase { int n; long long k; vector> A; // 1-indexed long long answer; }; mt19937_64 rng(42); TestCase gen_additive(int n, long long k) { // a[i][j] = i + j TestCase tc; tc.n = n; tc.k = k; tc.A.assign(n+1, vector(n+1, 0)); vector all; for (int i = 1; i <= n; i++) for (int j = 1; j <= n; j++) { tc.A[i][j] = i + j; all.push_back(i + j); } sort(all.begin(), all.end()); tc.answer = all[k-1]; return tc; } TestCase gen_multiplicative(int n, long long k) { // a[i][j] = i * j TestCase tc; tc.n = n; tc.k = k; tc.A.assign(n+1, vector(n+1, 0)); vector all; for (int i = 1; i <= n; i++) for (int j = 1; j <= n; j++) { tc.A[i][j] = (long long)i * j; all.push_back((long long)i * j); } sort(all.begin(), all.end()); tc.answer = all[k-1]; return tc; } TestCase gen_random_sorted(int n, long long k) { // Generate random sorted matrix TestCase tc; tc.n = n; tc.k = k; tc.A.assign(n+1, vector(n+1, 0)); // Start with a[i][j] = i + j, then add random increments for (int i = 1; i <= n; i++) for (int j = 1; j <= n; j++) tc.A[i][j] = (long long)i * 1000 + (long long)j * 1000; // Add random noise while maintaining sorted property // Simple: a[i][j] = i*1000 + j*1000 + random_prefix_sum // Actually let's just use i*n+j with some perturbation // Easiest: a[i][j] = random but sorted. Generate row by row. // Use: a[i][j] = base[i] + cumsum of random in row i, then adjust columns // Simplest correct approach: a[i][j] = i*C + j*D + small_random // where we ensure monotonicity long long C = 1000000, D = 1000; for (int i = 1; i <= n; i++) for (int j = 1; j <= n; j++) tc.A[i][j] = (long long)i * C + (long long)j * D + (rng() % 500); // Fix monotonicity: ensure row-sorted and col-sorted for (int i = 1; i <= n; i++) for (int j = 2; j <= n; j++) tc.A[i][j] = max(tc.A[i][j], tc.A[i][j-1]); for (int j = 1; j <= n; j++) for (int i = 2; i <= n; i++) tc.A[i][j] = max(tc.A[i][j], tc.A[i-1][j]); vector all; for (int i = 1; i <= n; i++) for (int j = 1; j <= n; j++) all.push_back(tc.A[i][j]); sort(all.begin(), all.end()); tc.answer = all[k-1]; return tc; } TestCase gen_uniform(int n, long long k) { // a[i][j] = i + j (lots of duplicates for small n) // Use: a[i][j] = (i-1)*n + j for no duplicates, perfectly spread TestCase tc; tc.n = n; tc.k = k; tc.A.assign(n+1, vector(n+1, 0)); // a[i][j] = i + j gives duplicates. Let's use that. vector all; for (int i = 1; i <= n; i++) for (int j = 1; j <= n; j++) { tc.A[i][j] = i + j; all.push_back(i + j); } sort(all.begin(), all.end()); tc.answer = all[k-1]; return tc; } TestCase gen_shifted(int n, long long k) { // a[i][j] = (i+n)*(j+n) - similar to interactor type 3 TestCase tc; tc.n = n; tc.k = k; tc.A.assign(n+1, vector(n+1, 0)); vector all; for (int i = 1; i <= n; i++) for (int j = 1; j <= n; j++) { tc.A[i][j] = (long long)(i + n) * (j + n); all.push_back(tc.A[i][j]); } sort(all.begin(), all.end()); tc.answer = all[k-1]; return tc; } // ---- Solution logic (extracted, no I/O) ---- struct Solver { const TestCase& tc; int query_count; vector memo; Solver(const TestCase& t) : tc(t), query_count(0) { memo.assign(2002 * 2002, -1); } long long do_query(int r, int c) { int key = r * 2001 + c; if (memo[key] != -1) return memo[key]; query_count++; memo[key] = tc.A[r][c]; return memo[key]; } long long solve() { int n = tc.n; long long k = tc.k; long long total = (long long)n * n; if (n == 1) return do_query(1, 1); // Heap for extreme k long long heap_k = min(k, total - k + 1); if (heap_k + n <= 24000) { if (k <= total - k + 1) { priority_queue, vector>, greater<>> pq; vector> vis(n + 1, vector(n + 1, false)); pq.emplace(do_query(1, 1), 1, 1); vis[1][1] = true; long long result = -1; for (long long i = 0; i < k; i++) { auto [v, r, c] = pq.top(); pq.pop(); result = v; if (r + 1 <= n && !vis[r + 1][c]) { vis[r + 1][c] = true; pq.emplace(do_query(r + 1, c), r + 1, c); } if (c + 1 <= n && !vis[r][c + 1]) { vis[r][c + 1] = true; pq.emplace(do_query(r, c + 1), r, c + 1); } } return result; } else { long long kk = total - k + 1; priority_queue> pq; vector> vis(n + 1, vector(n + 1, false)); pq.emplace(do_query(n, n), n, n); vis[n][n] = true; long long result = -1; for (long long i = 0; i < kk; i++) { auto [v, r, c] = pq.top(); pq.pop(); result = v; if (r - 1 >= 1 && !vis[r - 1][c]) { vis[r - 1][c] = true; pq.emplace(do_query(r - 1, c), r - 1, c); } if (c - 1 >= 1 && !vis[r][c - 1]) { vis[r][c - 1] = true; pq.emplace(do_query(r, c - 1), r, c - 1); } } return result; } } vector L(n + 1, 1), R(n + 1, n); long long k_rem = k; for (int iter = 0; iter < 100; iter++) { vector active; long long total_cand = 0; for (int i = 1; i <= n; i++) { if (L[i] <= R[i]) { active.push_back(i); total_cand += R[i] - L[i] + 1; } } int na = active.size(); if (total_cand == 0) break; if (total_cand == 1) { for (int i : active) return do_query(i, L[i]); break; } long long budget = 49500 - query_count; if (k_rem + na <= budget) { priority_queue, vector>, greater<>> pq; for (int i : active) pq.emplace(do_query(i, L[i]), i, L[i]); for (long long t = 1; t < k_rem; t++) { auto [v, r, c] = pq.top(); pq.pop(); if (c + 1 <= R[r]) pq.emplace(do_query(r, c + 1), r, c + 1); } return get<0>(pq.top()); } long long rev_k = total_cand - k_rem + 1; if (rev_k + na <= budget) { priority_queue> pq; for (int i : active) pq.emplace(do_query(i, R[i]), i, R[i]); for (long long t = 1; t < rev_k; t++) { auto [v, r, c] = pq.top(); pq.pop(); if (c - 1 >= L[r]) pq.emplace(do_query(r, c - 1), r, c - 1); } return get<0>(pq.top()); } // Pivot selection vector pvals; double target_frac = (double)(k_rem - 0.5) / total_cand; int sample_n = max(1, min(na, (int)ceil(sqrt((double)na) * 4))); int step = max(1, na / sample_n); for (int idx = 0; idx < na; idx += step) { int i = active[idx]; int width = R[i] - L[i] + 1; int col = L[i] + (int)(target_frac * width); col = max(L[i], min(R[i], col)); pvals.push_back(do_query(i, col)); } sort(pvals.begin(), pvals.end()); long long pivot = pvals[pvals.size() / 2]; vector p_le(n + 1, 0); { int j = 0; for (int idx = na - 1; idx >= 0; idx--) { int i = active[idx]; j = max(j, L[i]); while (j <= R[i] && do_query(i, j) <= pivot) j++; p_le[i] = j - 1; } } long long cle = 0; for (int i : active) { int rl = min(p_le[i], R[i]); if (rl >= L[i]) cle += rl - L[i] + 1; } if (cle >= k_rem) { for (int i : active) R[i] = min(R[i], p_le[i]); } else { k_rem -= cle; for (int i : active) L[i] = max(L[i], p_le[i] + 1); } } return -1; // shouldn't reach } }; int main() { struct TestDef { string name; function gen; }; vector tests; // Small tests tests.push_back({"additive n=100 k=5000", []{ return gen_additive(100, 5000); }}); tests.push_back({"multiplicative n=100 k=5000", []{ return gen_multiplicative(100, 5000); }}); // Medium tests tests.push_back({"additive n=500 k=125000", []{ return gen_additive(500, 125000); }}); tests.push_back({"multiplicative n=500 k=125000", []{ return gen_multiplicative(500, 125000); }}); tests.push_back({"random n=500 k=125000", []{ return gen_random_sorted(500, 125000); }}); // Hard tests (n=2000) tests.push_back({"additive n=2000 k=2000000", []{ return gen_additive(2000, 2000000); }}); tests.push_back({"multiplicative n=2000 k=2000000", []{ return gen_multiplicative(2000, 2000000); }}); tests.push_back({"shifted n=2000 k=2000000", []{ return gen_shifted(2000, 2000000); }}); tests.push_back({"random n=2000 k=2000000", []{ return gen_random_sorted(2000, 2000000); }}); // Extreme k tests.push_back({"multiplicative n=2000 k=1", []{ return gen_multiplicative(2000, 1); }}); tests.push_back({"multiplicative n=2000 k=4000000", []{ return gen_multiplicative(2000, 4000000); }}); tests.push_back({"multiplicative n=2000 k=100000", []{ return gen_multiplicative(2000, 100000); }}); tests.push_back({"multiplicative n=2000 k=3900000", []{ return gen_multiplicative(2000, 3900000); }}); for (auto& t : tests) { auto tc = t.gen(); Solver s(tc); long long result = s.solve(); bool correct = (result == tc.answer); double score; int n = tc.n; int used = s.query_count; if (!correct) score = 0.0; else if (used <= n) score = 1.0; else if (used >= 50000) score = 0.0; else score = (50000.0 - used) / (50000.0 - n); printf("%-45s n=%4d k=%8lld queries=%6d correct=%s score=%.4f\n", t.name.c_str(), tc.n, tc.k, used, correct ? "YES" : "NO", score); } return 0; }