#include using namespace std; struct TestCase { int n; long long k; vector> A; long long answer; }; mt19937_64 rng_gen(42); TestCase gen_matrix(int n, long long k, function valfn) { 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] = valfn(i, j); all.push_back(tc.A[i][j]); } sort(all.begin(), all.end()); tc.answer = all[k-1]; return tc; } TestCase gen_multiplicative(int n, long long k) { return gen_matrix(n, k, [](int i, int j) -> long long { return (long long)i * j; }); } TestCase gen_shifted(int n, long long k) { return gen_matrix(n, k, [n](int i, int j) -> long long { return (long long)(i + n) * (j + n); }); } TestCase gen_additive(int n, long long k) { return gen_matrix(n, k, [](int i, int j) -> long long { return i + j; }); } TestCase gen_random_sorted(int n, long long k) { TestCase tc; tc.n = n; tc.k = k; tc.A.assign(n+1, vector(n+1, 0)); for (int i = 1; i <= n; i++) for (int j = 1; j <= n; j++) tc.A[i][j] = (long long)i * 1000000 + (long long)j * 1000 + (rng_gen() % 500); 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; } struct Solver { const TestCase& tc; int query_count; vector memo; int n; Solver(const TestCase& t) : tc(t), query_count(0), n(t.n) { 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]; } // Staircase walk counting elements <= mid, respecting jLo/jHi bounds // jLo[i] = number of elements in row i KNOWN to be <= some lower bound (0-based count from left) // jHi[i] = number of elements in row i KNOWN to be <= some upper bound // Walk from top, j starts at jHi[1], goes down pair> countLeq(long long mid, const vector& jLo, const vector& jHi) { vector cutoff(n + 1, 0); long long cnt = 0; int j = min(n, jHi[1]); for (int i = 1; i <= n; i++) { int lo = jLo[i]; int hi = min(n, jHi[i]); if (hi <= lo) { cutoff[i] = lo; cnt += lo; continue; } if (j > hi) j = hi; while (j > lo) { long long v = do_query(i, j); if (v <= mid) { cutoff[i] = j; cnt += j; goto next; } j--; } cutoff[i] = lo; cnt += lo; next:; } return {cnt, cutoff}; } long long solve() { long long k = tc.k; long long NLL = (long long)n * n; if (n == 1) return do_query(1, 1); if (k == 1) return do_query(1, 1); if (k == NLL) return do_query(n, n); // Phase 1: Sample random values int countsBudget = min(30, max(1, 45000 / max(1, 2 * n))); int reserved = 100; long long left = 50000 - (long long)countsBudget * 2 * n - reserved; if (left < 0) left = 0; int E = (int)min(5000LL, max(400LL, left / 3)); long long SBudget = left - E; if (SBudget < 0) SBudget = 0; long long Ssize = min(SBudget, min(6000LL, (long long)n * n)); if (Ssize < 0) Ssize = 0; vector sampleVals; { mt19937_64 rng(1469598103934665603ULL ^ (uint64_t)n * 1181783497276652981ULL ^ ((uint64_t)k << 1)); set seen; // Grid sampling int g = (int)floor(sqrt((double)Ssize)); if (g > 0) { for (int ri = 1; ri <= g && (long long)sampleVals.size() < Ssize; ri++) { int r = max(1, min(n, (int)((ri * (long long)n) / (g + 1)))); for (int ci = 1; ci <= g && (long long)sampleVals.size() < Ssize; ci++) { int c = max(1, min(n, (int)((ci * (long long)n) / (g + 1)))); long long key = (long long)r * 10000 + c; if (seen.insert(key).second) sampleVals.push_back(do_query(r, c)); } } } // Random fill while ((long long)sampleVals.size() < Ssize) { int r = 1 + rng() % n; int c = 1 + rng() % n; long long key = (long long)r * 10000 + c; if (seen.insert(key).second) sampleVals.push_back(do_query(r, c)); } sort(sampleVals.begin(), sampleVals.end()); sampleVals.erase(unique(sampleVals.begin(), sampleVals.end()), sampleVals.end()); } // Phase 2: Binary search over sample values vector jLo(n + 1, 0), jHi(n + 1, n); long long cLo = 0, cHi = NLL; int li = -1, hiIndex = (int)sampleVals.size(); int usedCounts = 0; while (usedCounts < countsBudget && hiIndex - li > 1 && cHi - cLo > E) { int midIndex = li + (hiIndex - li) / 2; long long pivot = sampleVals[midIndex]; auto [cnt, cutoff] = countLeq(pivot, jLo, jHi); usedCounts++; if (cnt >= k) { hiIndex = midIndex; jHi = cutoff; cHi = cnt; } else { li = midIndex; jLo = cutoff; cLo = cnt; } } // Phase 3: Numeric binary search if still too wide long long loVal = (li >= 0 ? sampleVals[li] : (sampleVals.empty() ? do_query(1,1) : sampleVals.front())); long long hiVal = (hiIndex < (int)sampleVals.size() ? sampleVals[hiIndex] : (sampleVals.empty() ? do_query(n,n) : sampleVals.back())); while (usedCounts < countsBudget && cHi - cLo > E) { if (loVal >= hiVal) break; long long mid = loVal + (hiVal - loVal) / 2; if (mid == loVal) mid++; if (mid >= hiVal) break; auto [cnt, cutoff] = countLeq(mid, jLo, jHi); usedCounts++; if (cnt >= k) { jHi = cutoff; cHi = cnt; hiVal = mid; } else { jLo = cutoff; cLo = cnt; loVal = mid; } } // Phase 4: Enumerate remaining candidates long long W = cHi - cLo; vector cand; cand.reserve((size_t)W); for (int i = 1; i <= n; i++) { for (int j = jLo[i] + 1; j <= jHi[i]; j++) { cand.push_back(do_query(i, j)); } } long long rank = k - cLo; if (rank <= 0 || cand.empty()) return loVal; if (rank > (long long)cand.size()) return hiVal; nth_element(cand.begin(), cand.begin() + (rank - 1), cand.end()); return cand[rank - 1]; } }; int main() { struct TestDef { string name; function gen; }; vector tests; tests.push_back({"additive n=100 k=5000", []{ return gen_additive(100, 5000); }}); tests.push_back({"mult n=100 k=5000", []{ return gen_multiplicative(100, 5000); }}); tests.push_back({"additive n=500 k=125000", []{ return gen_additive(500, 125000); }}); tests.push_back({"mult n=500 k=125000", []{ return gen_multiplicative(500, 125000); }}); tests.push_back({"random n=500 k=125000", []{ return gen_random_sorted(500, 125000); }}); tests.push_back({"additive n=2000 k=2000000", []{ return gen_additive(2000, 2000000); }}); tests.push_back({"mult 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); }}); tests.push_back({"mult n=2000 k=100000", []{ return gen_multiplicative(2000, 100000); }}); tests.push_back({"mult 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); int used = s.query_count; double score = !correct ? 0.0 : (used <= tc.n ? 1.0 : (used >= 50000 ? 0.0 : (50000.0 - used) / (50000.0 - tc.n))); printf("%-45s q=%6d %s score=%.4f\n", t.name.c_str(), used, correct ? "OK" : "WRONG", score); } }