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Submission #492876

# Submission time Handle Problem Language Result Execution time Memory
492876 2021-12-09T12:46:20 Z czhang2718 Kangaroo (CEOI16_kangaroo) C++17
0 / 100
 2 ms 332 KB 
#include "bits/stdc++.h"
using namespace std;

const int MOD=1e9+7;
int n, s, e;
int dp[2001], dp2[2001];

int mult(int a, int b){
  return ((long long )a*b)%MOD;
}

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

int main(){
  cin.tie(0)->sync_with_stdio(0);
  freopen("kangaroo.in", "r", stdin);
  freopen("kangaroo.out", "w", stdout);

  cin >> n >> s >> e;

  dp[0]=1;
  for(int i=1; i<=n; i++){
    for(int j=0; j<i; j++){
      if(!dp[j]) continue;
      if(i==s || i==e){
        add(dp2[j+1], dp[j]);
        if(j) add(dp2[j], dp[j]);
        continue;
      }
      add(dp2[j+1], mult(dp[j], (j+1-(i>s)-(i>e))));
      if(j>=2) dp2[j-1]+=mult(dp[j], j-1);
    }
    for(int j=0; j<=i; j++){
      dp[j]=dp2[j];
      dp2[j]=0;
    }
  }
  cout << dp[1];
}

Compilation message

kangaroo.cpp: In function 'int main()':
kangaroo.cpp:20:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   20 |   freopen("kangaroo.in", "r", stdin);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
kangaroo.cpp:21:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   21 |   freopen("kangaroo.out", "w", stdout);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Subtask #1
0 / 6.0

# Verdict Execution time Memory Grader output
1 Incorrect 2 ms 332 KB Output isn't correct
2 Halted 0 ms 0 KB -

Subtask #2
0 / 30.0

# Verdict Execution time Memory Grader output
1 Incorrect 2 ms 332 KB Output isn't correct
2 Halted 0 ms 0 KB -

Subtask #3
0 / 15.0

# Verdict Execution time Memory Grader output
1 Incorrect 2 ms 332 KB Output isn't correct
2 Halted 0 ms 0 KB -

Subtask #4
0 / 49.0

# Verdict Execution time Memory Grader output
1 Incorrect 2 ms 332 KB Output isn't correct
2 Halted 0 ms 0 KB -