// Find the maximum step count achievable with n instructions and alphabet A // Use random sampling + hill climbing to maximize T #include using namespace std; constexpr long long P = 998244353; int n_instr, maxChar; int type_arr[30]; int pop_c[30], g1[30], push_c[30], g2[30]; optional> dp[30][1030]; bool vis[30][1030]; bool inf_flag; pair solve(int i, int x) { if (dp[i][x]) return dp[i][x].value(); if (vis[i][x]) { inf_flag = true; return {-1, 0}; } vis[i][x] = true; if (type_arr[i] == 0) { if (x == pop_c[i]) { dp[i][x] = {g1[i], 1LL}; } else { auto [j, u] = solve(g2[i], push_c[i]); if (inf_flag) return {-1, 0}; auto [k, v] = solve(j, x); if (inf_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(g2[i], push_c[i]); if (inf_flag) return {-1, 0}; auto [k, v] = solve(j, x); if (inf_flag) return {-1, 0}; dp[i][x] = {k, (u + v + 1) % P}; } } return dp[i][x].value(); } long long eval_prog() { for (int i = 0; i < n_instr; i++) for (int j = 0; j <= maxChar; j++) { dp[i][j].reset(); vis[i][j] = false; } inf_flag = false; auto [fi, steps] = solve(0, 0); if (inf_flag) return -1; return steps; } int main() { mt19937 rng(42); // For each (n, A), find max T achievable for (int n = 2; n <= 10; n++) { for (int A : {n, n+2, 2*n, 3*n, min(30, 5*n)}) { n_instr = n; maxChar = A; long long global_max = 0; for (int restart = 0; restart < 10000; restart++) { // Random program for (int i = 0; i < n; i++) { type_arr[i] = (i == n-1) ? 1 : 0; if (type_arr[i] == 0) { pop_c[i] = 1 + rng() % A; g1[i] = rng() % n; push_c[i] = 1 + rng() % A; g2[i] = rng() % n; } else { push_c[i] = 1 + rng() % A; g2[i] = rng() % n; } } long long T = eval_prog(); if (T < 0) continue; // Hill climb to maximize T for (int iter = 0; iter < 5000; iter++) { int i = rng() % n; int sv_pop = pop_c[i], sv_g1 = g1[i], sv_push = push_c[i], sv_g2 = g2[i]; int what = rng() % 4; if (what == 0 && type_arr[i] == 0) pop_c[i] = 1 + rng() % A; else if (what == 1) push_c[i] = 1 + rng() % A; else if (what == 2) g2[i] = rng() % n; else if (type_arr[i] == 0) g1[i] = rng() % n; long long nT = eval_prog(); if (nT > T) T = nT; else { pop_c[i] = sv_pop; g1[i] = sv_g1; push_c[i] = sv_push; g2[i] = sv_g2; } } if (T > global_max) global_max = T; } printf("n=%d A=%d: maxT=%lld (chain max=%lld, P=%d)\n", n, A, global_max, min((1LL<<(n))-1, (long long)P), P); } } return 0; }