Submission #94965

#	Time	Username	Problem	Language	Result	Execution time	Memory
94965		jasony123123	Kangaroo (CEOI16_kangaroo)	C++11	100 / 100	38 ms	31736 KiB

kangaroo

#define _CRT_SECURE_NO_WARNINGS
#include <bits/stdc++.h>
//#include <ext/pb_ds/tree_policy.hpp>
//#include <ext/pb_ds/assoc_container.hpp>
using namespace std;
//using namespace __gnu_pbds;

#define FOR(i,start,end) for(int i=start;i<(int)(end);i++)
#define FORE(i,start,end) for(int i=start;i<=(int)end;i++)
#define RFOR(i,start,end) for(int i = start; i>end; i--)
#define RFORE(i,start,end) for(int i = start; i>=end; i--)
#define all(a) a.begin(), a.end()
#define mt make_tuple
#define mp make_pair
#define v vector
#define sf scanf
#define pf printf
#define dvar(x) cout << #x << " := " << x << "\n"
#define darr(x,n) FOR(i,0,n) cout << #x << "[" << i << "]" << " := " << x[i] << "\n"

typedef long long ll;
typedef long double ld;
typedef pair<int, int > pii;
typedef pair<ll, ll> pll;
//template <class T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<class T> void minn(T &a, T b) { a = min(a, b); }
template<class T> void maxx(T &a, T b) { a = max(a, b); }

void io() {
#ifdef LOCAL_PROJECT 
	freopen("input.in", "r", stdin); freopen("output.out", "w", stdout);
#else 
	/* online submission */

#endif 
	ios_base::sync_with_stdio(false); cin.tie(NULL);
}

const ll MOD = 1000000007LL;
const ll PRIME = 105943LL;
const ll INF = 1e18;
/********************CEOI 2016 Day 1 Problem 2******************************/

inline ll add(ll a, ll b) { return (a + b) % MOD; }
inline ll mul(ll a, ll b) { return (1LL * a*b) % MOD; }

int n, a, b;
ll dp[2001][2001];

int main() {
	io();
	cin >> n >> a >> b;
	dp[1][1] = 1;
	int av = 2;
	if (a == 1 || b == 1)
		av--;
	FORE(i, 2, n) {
		if (i == a || i == b) {
			av--;
			FORE(j, 1, n)
				dp[i][j] = add(dp[i - 1][j - 1], dp[i - 1][j]);
		}
		else {
			FORE(j, 1, n)
				dp[i][j] = add(dp[i - 1][j + 1] * j, dp[i - 1][j - 1] * (j - 2 + av));
		}
	}
	cout << dp[n][1] << "\n";
}

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