Yuki 623 fudan no modulus to tigau
Problem Description:
Given Q queries of X's, compute f(X), modulo 998244353.
Constraints:
2≤n≤50
1≤q≤50
0≤ai,bi≤i - 1
0≤xi≤998244352
Solution:
Compute each query independently, the only variant is n (relevantly small), so we can apply DP.
Code:
#include <bits/stdc++.h> const int MOD = 998244353; signed main() { std::ios::sync_with_stdio(false); int N; std::cin >> N; std::vector<int> T(N + 1), A(N + 1), B(N + 1); for (int i = 2; i <= N; ++i) { std::cin >> T[i] >> A[i] >> B[i]; } int Q; std::cin >> Q; while (Q--) { int X; std::cin >> X; std::vector<int> dp(N + 1, -1); std::function<int(int, int)> f = [&](int n, int x) { if (n == 0) return 1; if (n == 1) return x; if (~dp[n]) return dp[n]; if (T[n] == 1) return dp[n] = (f(A[n], x) + f(B[n], x)) % MOD; if (T[n] == 2) return dp[n] = 1LL * A[n] * f(B[n], x) % MOD; return dp[n] = 1LL * f(A[n], x) * f(B[n], x) % MOD; }; std::cout << f(N, X) << std::endl; } return 0; }