Submission #685021

#	Time	Username	Problem	Language	Result	Execution time	Memory
685021		NeroZein	Kangaroo (CEOI16_kangaroo)	C++14	0 / 100	2082 ms	596 KiB

kangaroo

/*
 *    author: NeroZein
 *    created: 23.01.2023 08:16:46
*/
#include <bits/stdc++.h>
using namespace std;

const int md = 1e9+7;

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

inline int mul(int a, int b){
	return (int)((long long) a * b % md);
}

signed main(){
	freopen("kangaroo.in", "r", stdin);
	freopen("kangaroo.out", "w", stdout);
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int n, cs, cf;
	cin >> n >> cs >> cf;
	vector<int> dp(n);
	dp[1] = 1; 
	for (int i = 2; i <= n; ++i){
		vector<int> pd(n); 
		for (int j = 1; j <= n; ++j){
			//endpoint either 
			if(i == cs || i == cf){
				//alone or to the left or right to existing set
				pd[j] = add(dp[j-1], dp[j]);
			}
			else{
				//merge two sets or start a new one
				pd[j] = add(mul(j, dp[j+1]), mul(j - (i > cs) - (i > cf), dp[j-1]));
			}
		}
		swap(dp, pd);
	}
	cout << dp[1]; 
}

Compilation message (stderr)

kangaroo.cpp: In function 'int main()':
kangaroo.cpp:23:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   23 |  freopen("kangaroo.in", "r", stdin);
      |  ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
kangaroo.cpp:24:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   24 |  freopen("kangaroo.out", "w", stdout);
      |  ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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