Submission #474834

#	Time	Username	Problem	Language	Result	Execution time	Memory
474834		ntabc05101	Kangaroo (CEOI16_kangaroo)	C++14	100 / 100	40 ms	15948 KiB

kangaroo

#include<bits/stdc++.h>
using namespace std;

#define taskname "kangaroo"

const int mxN = 2000;
const int mod = 1e9 + 7;

int n, cs, cf;
int dp[mxN + 5][mxN + 5];

int main() {
  if (fopen(taskname".inp", "r")) {
    freopen(taskname".inp", "r", stdin);
    freopen(taskname".out", "w", stdout);
  }

  cin.tie(0)->sync_with_stdio(0);

  cin >> n >> cs >> cf;
  dp[1][1] = 1;
  for (int i = 2; i <= n; i++) {
    for (int j = 1; j <= n; j++) {
      if (i == cs || i == cf) {
        dp[i][j] = (dp[i - 1][j - 1] + dp[i - 1][j]) % mod;
      }
      else {
        dp[i][j] = 1ll * dp[i - 1][j + 1] * j % mod;
        (dp[i][j] += 1ll * dp[i - 1][j - 1] * (j - (i > cs) - (i > cf)) % mod) %= mod;
      }
    }
  }

  cout << dp[n][1] << "\n";

  return 0;
}

Compilation message (stderr)

kangaroo.cpp: In function 'int main()':
kangaroo.cpp:14:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   14 |     freopen(taskname".inp", "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
kangaroo.cpp:15:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   15 |     freopen(taskname".out", "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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