Submission #1303912

#	Time	Username	Problem	Language	Result	Execution time	Memory
1303912		hoa208	Kangaroo (CEOI16_kangaroo)	C++20	6 / 100	44 ms	94584 KiB

kangaroo

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define FOR(i, a, b) for (int i = (a), _b = (b); i <= _b; i++)
#define FORD(i, b, a) for (int i = (b), _a = (a); i >= _a; i--)
#define pa pair<ll, ll>
#define fi first
#define se second
#define bit(mask, j) ((mask >> j) & 1)
const   ll mod = 1e9 + 7;
const   ll INF = 1e18;
//--------------------------------------------------------------------

ll s, t;
ll n;
const ll N = 2003;
ll f[N][N][3];
ll calc(ll i, ll j, ll c) {
	if(i == n + 1) return j == 1;
	ll res = 0;
	if(f[i][j][c] != -1) return f[i][j][c];
	if(i == s || i == t) {
		if(j != 0)
		res += calc(i + 1, j, c + 1);
		res += calc(i + 1, j + 1, c + 1);
	}
	else {
		res += calc(i + 1, j + 1, c) * (j + 1 - c);
		if(j >= 2)
			res += calc(i + 1, j - 1, c) * (j - 1);
	}
	return f[i][j][c] = res;
}
void hbmt() {
	memset(f, -1, sizeof f);
	cin >> n >> s >> t;
	cout << calc(1, 0, 0);
}

int main() {
	
	ios_base::sync_with_stdio(0);
	cin.tie(0);cout.tie(0);

	#define NAME "hbmt"
	if(fopen(NAME".inp", "r")) {
		freopen(NAME".inp", "r", stdin);
		freopen(NAME".out", "w", stdout);
	}
	
	//int t;cin>>t;while(t--)
	hbmt();
	return 0;
}

Compilation message (stderr)

kangaroo.cpp: In function 'int main()':
kangaroo.cpp:47:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   47 |                 freopen(NAME".inp", "r", stdin);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
kangaroo.cpp:48:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   48 |                 freopen(NAME".out", "w", stdout);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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