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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. int main() {
  5.     ios::sync_with_stdio(false);
  6.     cin.tie(nullptr);
  7.     const int MOD = 998244353;
  8.  
  9.     int N;
  10.     if(!(cin >> N)) return 0;
  11.     vector<int> A(N + 1);
  12.     for (int i = 1; i <= N; ++i) cin >> A[i];
  13.  
  14.     vector<int> p2(N + 3, 1);
  15.     for (int i = 1; i < (int)p2.size(); ++i) p2[i] = (p2[i - 1] * 2LL) % MOD;
  16.  
  17.     vector<int> nxt0(N + 3, 1), nxt1(N + 3, 1);
  18.  
  19.     for (int i = N; i >= 2; --i) {
  20.         vector<int> cur0(N + 3), cur1(N + 3);
  21.         cur0[0] = cur1[0] = 0;
  22.         bool asc = A[i - 1] < A[i];
  23.         for (int q = 1; q <= N; ++q) {
  24.             int pop = cur1[q - 1];
  25.             int add = (long long)p2[q - 1] * nxt0[q + 1] % MOD;
  26.             cur1[q] = (pop + add) % MOD;
  27.             cur0[q] = pop;
  28.             if (asc) cur0[q] = (cur0[q] + add) % MOD;
  29.         }
  30.         nxt0.swap(cur0);
  31.         nxt1.swap(cur1);
  32.     }
  33.  
  34.     cout << nxt1[1] % MOD << '\n';
  35.     return 0;
  36. }
  37.  
Success #stdin #stdout 0.01s 5308KB
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https://ideone.com/KrZ5SX
language:
C++14 (gcc 8.3)
created:
13 days ago
visibility:
public

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