#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; } // Simulating gpt5.2_2 approach exactly 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 get(int x, int y) { int key = x * 2001 + y; if (memo[key] != -1) return memo[key]; query_count++; memo[key] = tc.A[x][y]; return memo[key]; } pair> count_leq(long long x) { vector pos(n + 1, 0); long long cnt = 0; int j = n; for (int i = 1; i <= n; i++) { while (j >= 1) { if (get(i, j) <= x) break; j--; } pos[i] = j; cnt += j; if (j == 0) break; } return {cnt, pos}; } pair> count_lt(long long x) { vector pos(n + 1, 0); long long cnt = 0; int j = n; for (int i = 1; i <= n; i++) { while (j >= 1) { if (get(i, j) < x) break; j--; } pos[i] = j; cnt += j; if (j == 0) break; } return {cnt, pos}; } long long solve() { long long k = tc.k; long long N2 = (long long)n * n; if (n == 1) return get(1, 1); if (k <= 1) return get(1, 1); if (k >= N2) return get(n, n); // Heap for small k long long tSmall = min(k, N2 - k + 1); if (tSmall + n <= 49000) { if (k <= N2 - k + 1) { priority_queue, vector>, greater<>> pq; for (int i = 1; i <= n; i++) pq.emplace(get(i, 1), i, 1); long long ans = 0; for (long long s = 1; s <= k; s++) { auto [v, r, c] = pq.top(); pq.pop(); ans = v; if (s == k) break; if (c < n) pq.emplace(get(r, c + 1), r, c + 1); } return ans; } else { priority_queue> pq; for (int i = 1; i <= n; i++) pq.emplace(get(i, n), i, n); long long ans = 0; long long t = N2 - k + 1; for (long long s = 1; s <= t; s++) { auto [v, r, c] = pq.top(); pq.pop(); ans = v; if (s == t) break; if (c > 1) pq.emplace(get(r, c - 1), r, c - 1); } return ans; } } mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count()); // Initial upper bound int rBound = max(1, min(n, (int)((k + n - 1) / n))); long long highTh = get(rBound, n); auto [cntHigh, posHigh] = count_leq(highTh); if (cntHigh < k) { highTh = get(n, n); tie(cntHigh, posHigh) = count_leq(highTh); } vector posLow(n + 1, 0); long long cntLow = 0; long long lowTh = LLONG_MIN; const int SAMPLES = 9; while (true) { if (cntHigh < k) { highTh = get(n, n); tie(cntHigh, posHigh) = count_leq(highTh); if (cntHigh < k) break; } long long candTotal = cntHigh - cntLow; if (candTotal <= 0) return highTh; long long needSmall = k - cntLow; long long needLarge = cntHigh - k + 1; vector pref(n + 1, 0); int nonempty = 0; for (int i = 1; i <= n; i++) { int len = posHigh[i] - posLow[i]; if (len > 0) nonempty++; pref[i] = pref[i - 1] + max(0, len); } candTotal = pref[n]; if (candTotal <= 0) return highTh; long long remaining = 49500 - query_count; long long enumCost = min(needSmall, needLarge) + nonempty + 10; if (enumCost <= remaining) { // Enumerate if (needSmall <= needLarge) { priority_queue, vector>, greater<>> pq; for (int i = 1; i <= n; i++) { int L = posLow[i] + 1, R = posHigh[i]; if (L >= 1 && L <= n && L <= R) pq.emplace(get(i, L), i, L); } long long ans = 0; for (long long t = 1; t <= needSmall; t++) { auto [v, r, c] = pq.top(); pq.pop(); ans = v; if (t == needSmall) break; if (c < posHigh[r]) pq.emplace(get(r, c + 1), r, c + 1); } return ans; } else { priority_queue> pq; for (int i = 1; i <= n; i++) { int L = posLow[i] + 1, R = posHigh[i]; if (R >= 1 && R <= n && L <= R) pq.emplace(get(i, R), i, R); } long long ans = 0; for (long long t = 1; t <= needLarge; t++) { auto [v, r, c] = pq.top(); pq.pop(); ans = v; if (t == needLarge) break; if (c > posLow[r] + 1) pq.emplace(get(r, c - 1), r, c - 1); } return ans; } } if (remaining < 2 * n + SAMPLES + 200) { if (nonempty + min(needSmall, needLarge) + 10 <= remaining) { // same enum if (needSmall <= needLarge) { priority_queue, vector>, greater<>> pq; for (int i = 1; i <= n; i++) { int L = posLow[i] + 1, R = posHigh[i]; if (L >= 1 && L <= n && L <= R) pq.emplace(get(i, L), i, L); } long long ans = 0; for (long long t = 1; t <= needSmall; t++) { auto [v, r, c] = pq.top(); pq.pop(); ans = v; if (t == needSmall) break; if (c < posHigh[r]) pq.emplace(get(r, c + 1), r, c + 1); } return ans; } else { priority_queue> pq; for (int i = 1; i <= n; i++) { int L = posLow[i] + 1, R = posHigh[i]; if (R >= 1 && R <= n && L <= R) pq.emplace(get(i, R), i, R); } long long ans = 0; for (long long t = 1; t <= needLarge; t++) { auto [v, r, c] = pq.top(); pq.pop(); ans = v; if (t == needLarge) break; if (c > posLow[r] + 1) pq.emplace(get(r, c - 1), r, c - 1); } return ans; } } return highTh; } // Sample pivots vector samp; for (int s = 0; s < SAMPLES; s++) { long long pick = 1 + rng() % candTotal; int row = (int)(lower_bound(pref.begin() + 1, pref.end(), pick) - pref.begin()); if (row < 1 || row > n) continue; int len = posHigh[row] - posLow[row]; if (len <= 0) continue; int col = posLow[row] + 1 + rng() % len; col = max(1, min(n, col)); samp.push_back(get(row, col)); } if (samp.empty()) return highTh; sort(samp.begin(), samp.end()); double q = (double)needSmall / (double)candTotal; int idx = (int)(q * (double)(samp.size() - 1)); idx = max(0, min((int)samp.size() - 1, idx)); long long pivot = samp[idx]; auto [cntPivot, posPivot] = count_leq(pivot); if (cntPivot >= k) { if (pivot == highTh && cntPivot == cntHigh) { auto [cntLess, posLess] = count_lt(pivot); if (cntLess < k) return pivot; highTh = pivot - 1; posHigh = posLess; cntHigh = cntLess; } else { highTh = pivot; posHigh = posPivot; cntHigh = cntPivot; } } else { lowTh = pivot; posLow = posPivot; cntLow = cntPivot; } } return 0; } }; 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); } }