Submission #869032

#	Time	Username	Problem	Language	Result	Execution time	Memory
869032		mgl_diamond	Kangaroo (CEOI16_kangaroo)	C++17	0 / 100	0 ms	604 KiB

kangaroo

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ii = pair<int, int>;

#define foru(i, l, r) for(int i=(l); i<=(r); ++i)
#define ford(i, l, r) for(int i=(l); i>=(r); --i)
#define fore(x, v) for(auto &x : v)
#define all(x) (x).begin(), (x).end()
#define sz(x) (int)x.size()

void setIO() {
  ios::sync_with_stdio(0);
  cin.tie(0); cout.tie(0);
  if (fopen("input.inp", "r")) {
    freopen("input.inp", "r", stdin);
    freopen("input.out", "w", stdout);
  }
}

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int MOD = 1e9+7;
int n, s, t, dp[2][2002][3][3];

void add(int &a, int b) {
  a += b;
  if (a >= MOD) a -= MOD;
}

int mul(int a, int b) {
  return 1LL * a * b % MOD;
}

int main() {
  setIO();
  cin >> n >> s >> t;

  int cur = 0, nxt = 1;
  memset(dp[cur], 0, sizeof(dp[cur]));
  dp[cur][0][0][0] = 1;

  foru(i, 0, n-1) {
    memset(dp[nxt], 0, sizeof(dp[nxt]));
    foru(j, 0, i) {
      foru(x, 0, 2) {
        foru(y, 0, 2) if (dp[cur][j][x][y] > 0) {
          int val = dp[cur][j][x][y];
//          cout << i << " " << j << " " << x << " " << y << " " << val << "\n";

          if (i+1 == s) {
            add(dp[nxt][j][1][y], val);
            if (j > 0) add(dp[nxt][j-1][1][y], mul(val, j));
            continue;
          }

          if (i+1 == t) {
            add(dp[nxt][j][x][1], val);
            if (j > 0) add(dp[nxt][j-1][x][1], mul(val, j));
            continue;
          }

          // new comp type 0
          add(dp[nxt][j+1][x][y], val);

          // comb with type 0
          add(dp[nxt][j][x][y], mul(val, j));

          // comb with type 1
          if (x) add(dp[nxt][j-1][1][y], mul(val, j));

          // comb with type 2
          if (y) add(dp[nxt][j-1][x][1], mul(val, j));
        }
      }
    }

    cur ^= 1; nxt ^= 1;
  }

  cout << dp[cur][0][1][1];
}

Compilation message (stderr)

kangaroo.cpp: In function 'void setIO()':
kangaroo.cpp:16:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   16 |     freopen("input.inp", "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
kangaroo.cpp:17:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   17 |     freopen("input.out", "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 6
• Subtask 2: 0 / 30
• Subtask 3: 0 / 15
• Subtask 4: 0 / 49