Submission #806989

#	Time	Username	Problem	Language	Result	Execution time	Memory
806989		nonono	Kangaroo (CEOI16_kangaroo)	C++14	100 / 100	18 ms	22996 KiB

kangaroo

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

const int mod = 1e9 + 7;
const int mxN = 2005;

int n, s, f;
int dp[mxN][mxN];

signed main() {
    #define taskname ""

    if(fopen(taskname".inp", "r")) {
        freopen(taskname".inp", "r", stdin);
        freopen(taskname".out", "w", stdout);
    }
    
    cin.tie(0)->sync_with_stdio(0);
    
    cin >> n >> s >> f;
    
    dp[1][1] = 1;
    for(int i = 1; i < n; i ++) {
        int x = (i + 1 >= s) + (i + 1 >= f);
        
        for(int j = 1; j <= i; j ++) {
            if(i + 1 == s || i + 1 == f) {
                dp[i + 1][j] += dp[i][j];
                dp[i + 1][j + 1] += dp[i][j];
                continue ;
            }
            
            (dp[i + 1][j + 1] += dp[i][j] * (j + 1 - x)) %= mod;
            (dp[i + 1][j - 1] += dp[i][j] * (j - 1)) %= mod;
        }
    }
    
    cout << dp[n][1] << "\n";
    return 0;
}

Compilation message (stderr)

kangaroo.cpp: In function 'int main()':
kangaroo.cpp:15:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   15 |         freopen(taskname".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
kangaroo.cpp:16:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   16 |         freopen(taskname".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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