Submission #975491

#	Time	Username	Problem	Language	Result	Execution time	Memory
975491		duckindog	Kangaroo (CEOI16_kangaroo)	C++17	6 / 100	7 ms	31904 KiB

kangaroo

#include <bits/stdc++.h>

using namespace std;

#define int long long

const int N = 2'000 + 10,
          M = 1'000'000'007;
int n, st, ed;

struct modint { 
  int value;
  
  modint(int x = 0) : value(x) {}

  modint operator + (const modint& rhs) { return (value + rhs.value) % M; }
  modint operator - (const modint& rhs) { return ((value - rhs.value) % M + M) % M; }
  modint operator * (const modint& rhs) { return 1ll * value * rhs.value % M; }

  modint operator += (const modint& rhs) { value = (value + rhs.value) % M; return *this; }
  modint operator -= (const modint& rhs) { value = ((value - rhs.value) % M + M) % M; return *this; }
  modint operator *= (const modint& rhs) { value = 1ll * value * rhs.value % M; return *this; }

  friend ostream& operator << (ostream& os, const auto& rhs) { return os << rhs.value; }
} f[N][N];

int32_t main() { 
  cin.tie(0)->sync_with_stdio(0);

  cin >> n >> st >> ed;

  f[1][1] = 1;
  for (int i = 2; i <= n; ++i) { 
    for (int j = 1; j <= i; ++j) { 
      auto& ret = f[i][j];

      if (i == st || i == ed) ret = f[i - 1][j] + f[i][j - 1];
      else ret = f[i - 1][j + 1] * j + f[i - 1][j - 1] * (j - (i > st) - (i > ed));
    }
  }

  cout << f[n][1] << "\n";
}

Compilation message (stderr)

kangaroo.cpp:24:51: warning: use of 'auto' in parameter declaration only available with '-fconcepts-ts'
   24 |   friend ostream& operator << (ostream& os, const auto& rhs) { return os << rhs.value; }
      |                                                   ^~~~

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