제출 #575716

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
575716		hoainiem	캥거루 (CEOI16_kangaroo)	C++14	100 / 100	38 ms	16244 KiB

kangaroo

#include <bits/stdc++.h>
//#pragma GCC target("popcnt")
#define fi first
#define se second
#define lc id<<1
#define rc id<<1^1
#define val f[i][j]
const int mod = 1e9 + 7;
double begintime, endtime;

using namespace std;
inline void CALC_TIME()
{
    endtime = clock();
    cout << "\nexecution time : " << (endtime - begintime + 1) / 1000 << " s";
}
void add(int &x, int y)
{
    x += y;
    if (x >= mod)
        x -= mod;
}
int mul(int x, int y)
{
    return 1LL * x * y % mod;
}
typedef pair<int, int> pii;
int n, cs, cf;
int f[2008][2008];
int dq(int i, int j)
{
    if (val != -1)
        return val;
    if (i == n)
        return val = (j == 1);
    int res = 0;
    if (i + 1 == cs || i + 1 == cf)
    {
        add(res, dq(i + 1, j));
        add(res, dq(i + 1, j + 1));
        return val = res;
    }
    if (j > 1)
        add(res, mul(j - 1, dq(i + 1, j - 1)));
    add(res, mul(j + 1 - (i + 1 > cs) - (i + 1 > cf), dq(i + 1, j + 1)));
    return val = res;
}
int main()
{
    begintime = clock();
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    memset(f, -1, sizeof(f));
    cin >> n >> cs >> cf;
    cout << dq(0, 0);
    return 0;
}

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