// For n=2..6, find the maximum step count achievable with various alphabet sizes // Use random search for speed #include using namespace std; constexpr long long P = 998244353; int n_instr; int maxChar; int type_arr[30]; int pop_char_arr[30], goto1_arr[30], push_char_arr[30], goto2_arr[30]; optional> dp[30][110]; bool vis[30][110]; bool infinite_flag; pair solve(int i, int x) { if (dp[i][x]) return dp[i][x].value(); if (vis[i][x]) { infinite_flag = true; return {-1, 0}; } vis[i][x] = true; if (type_arr[i] == 0) { if (x == pop_char_arr[i]) { dp[i][x] = {goto1_arr[i], 1LL}; } else { auto [j, u] = solve(goto2_arr[i], push_char_arr[i]); if (infinite_flag) return {-1, 0}; auto [k, v] = solve(j, x); if (infinite_flag) return {-1, 0}; dp[i][x] = {k, (u + v + 1) % P}; } } else { if (x == 0) { dp[i][x] = {-1, 1LL}; } else { auto [j, u] = solve(goto2_arr[i], push_char_arr[i]); if (infinite_flag) return {-1, 0}; auto [k, v] = solve(j, x); if (infinite_flag) return {-1, 0}; dp[i][x] = {k, (u + v + 1) % P}; } } return dp[i][x].value(); } long long evaluate() { for (int i = 0; i < n_instr; i++) for (int j = 0; j <= maxChar; j++) { dp[i][j].reset(); vis[i][j] = false; } infinite_flag = false; auto [fi, steps] = solve(0, 0); if (infinite_flag) return -1; return steps; } int main() { mt19937 rng(42); for (int n = 2; n <= 8; n++) { for (int alpha = 1; alpha <= min(20, n*3); alpha++) { n_instr = n; maxChar = alpha; long long max_steps = 0; for (int trial = 0; trial < 200000; trial++) { for (int i = 0; i < n_instr; i++) { if (i == n_instr - 1) type_arr[i] = 1; else type_arr[i] = (rng() % 3 == 0) ? 1 : 0; if (type_arr[i] == 0) { pop_char_arr[i] = 1 + rng() % maxChar; goto1_arr[i] = rng() % n_instr; push_char_arr[i] = 1 + rng() % maxChar; goto2_arr[i] = rng() % n_instr; } else { push_char_arr[i] = 1 + rng() % maxChar; goto2_arr[i] = rng() % n_instr; } } long long T = evaluate(); if (T > max_steps) max_steps = T; } printf("n=%d alpha=%d maxT=%lld chain_max=%lld\n", n, alpha, max_steps, (1LL<<(n))-1); } } return 0; }