mirror of
https://git.sb/baoshuo/OI-codes.git
synced 2024-12-25 06:51:58 +00:00
65 lines
1.3 KiB
C++
65 lines
1.3 KiB
C++
#include <iostream>
|
|
#include <algorithm>
|
|
#include <cstring>
|
|
#include <iterator>
|
|
#include <utility>
|
|
#include <vector>
|
|
|
|
using std::cin;
|
|
using std::cout;
|
|
const char endl = '\n';
|
|
|
|
const int N = 105;
|
|
const int mod = 998244353;
|
|
|
|
int n, a[N], p[N], f[N][N][N];
|
|
std::vector<std::pair<int, int>> nums;
|
|
|
|
int solve(int l, int r, int x) {
|
|
if (x == 0) return 1;
|
|
if (l == r) return 1;
|
|
if (f[l][r][x] != -1) return f[l][r][x];
|
|
|
|
int pos = std::find(p + l, p + r + 1, x) - p;
|
|
|
|
if (pos > r) {
|
|
return f[l][r][x] = solve(l, r, x - 1);
|
|
}
|
|
|
|
int res = 0;
|
|
|
|
for (int i = pos; i <= r; i++) {
|
|
if (p[i] <= x) {
|
|
res = (res + static_cast<long long>(solve(l, i, x - 1)) * solve(i + 1, r, x) % mod) % mod;
|
|
}
|
|
}
|
|
|
|
return f[l][r][x] = res;
|
|
}
|
|
|
|
int main() {
|
|
std::ios::sync_with_stdio(false);
|
|
cin.tie(nullptr);
|
|
|
|
cin >> n;
|
|
|
|
for (int i = 1; i <= n; i++) {
|
|
cin >> a[i];
|
|
|
|
nums.emplace_back(a[i], i);
|
|
}
|
|
|
|
std::sort(nums.begin(), nums.end());
|
|
nums.erase(std::unique(nums.begin(), nums.end()), nums.end());
|
|
|
|
for (int i = 1; i <= n; i++) {
|
|
p[i] = std::distance(nums.begin(), std::lower_bound(nums.begin(), nums.end(), std::pair<int, int>{a[i], i}));
|
|
}
|
|
|
|
memset(f, 0xff, sizeof(f));
|
|
|
|
cout << solve(1, n, n) << endl;
|
|
|
|
return 0;
|
|
}
|