Submission #127391

#	Time	Username	Problem	Language	Result	Execution time	Memory
127391		RockyB	Tents (JOI18_tents)	C++17	48 / 100	624 ms	107128 KiB

tents

#include <bits/stdc++.h>

#define rep(a, b, c) for (int a = (b); (b) <= (c); a++)
#define per(a, b, c) for (int a = (b); (b) >= (c); a--)

#define nl '\n'
#define ioi exit(0);

const int mod = (int)1e9 + 7;

using namespace std;

void add(int &x, int y) {
  x += y;
  if (x >= mod) x -= mod;
  if (x < 0) x += mod;
}
int sum(int x, int y) {
  add(x, y);
  return x;
}

int n, m;

int dp[301][301][301];
inline int calc(int v = 1, int free = m, int must = 0) {
  if (v > n) return 1;
  if (~dp[v][free][must]) return dp[v][free][must];
  int res = calc(v + 1, free, must);
  // put < or > or ^
  if (free > 0) add(res, calc(v + 1, free - 1, must) * 1ll * free * 3 % mod);
  // connect v and ^
  if (must > 0) add(res, calc(v + 1, free, must - 1) * 1ll * must % mod);
  // open v
  if (free > 0) add(res, calc(v + 1, free - 1, must + 1) * 1ll * free % mod);
  // connect > and <
  if (free > 1) add(res, calc(v + 1, free - 2, must) * 1ll * (free * (free - 1) / 2) % mod);
  return dp[v][free][must] = res;
}
int main() {
  #ifdef IOI
    freopen ("in.txt", "r", stdin);
  #endif
  cin >> n >> m;
  memset(dp, -1, sizeof(dp));
  cout << sum(-1, calc()) << nl;
  ioi
}

• Subtask 1: 48 / 48
• Subtask 2: 0 / 52