Submission #1093612

#	Time	Username	Problem	Language	Result	Execution time	Memory
1093612		Mike_Vu	Kangaroo (CEOI16_kangaroo)	C++14	100 / 100	17 ms	16200 KiB

kangaroo

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef long double dou;
#define pii pair<int, int>
#define fi first
#define se second
#define pb push_back
#define MASK(x) (1LL<<(x))
#define BIT(x, j) (((x)>>(j))&1)

template<typename T> bool maximize(T &x, const T &y) {
    if (x < y) {x = y; return 1;}
    return 0;
}
template<typename T> bool minimize(T &x, const T &y) {
    if (x > y) {x = y; return 1;}
    return 0;
}

namespace modulofunc{
    const int mod = 1e9+7;
    void ad(int &x, int y) {
        ll temp = x+y;
        if (temp >= mod) temp -= mod;
        x = temp;
    }
    int add(int x, int y) {
        ll temp = x+y;
        if (temp >= mod) temp -= mod;
        return temp;
    }
    int sub(int x, int y) {
        ll temp = x-y;
        if (temp < 0) temp += mod;
        return temp;
    }
    int mul(int x, int y) {
        return 1LL*x*y%mod;
    }
}
using namespace modulofunc;

const int maxn = 2005;
int n, cs, cf;
int dp[maxn][maxn];

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
//    #define name "task"
//    if (fopen(name".inp", "r")) {
//        freopen(name".inp", "r", stdin);
//        freopen(name".out", "w", stdout);
//    }
    cin >> n >> cs >> cf;
    memset(dp, 0, sizeof(dp));
    dp[0][0] = 1;
    for (int i = 0; i < n; i++) {
        for (int j = 0; j <= i; j++) {
            if (!dp[i][j]) continue;
            if (i+1 == cs || i+1 == cf) {
                ad(dp[i+1][j], dp[i][j]); //join >
                ad(dp[i+1][j+1], dp[i][j]); //new <
            }
            else {
                //join
                if (i > 1) ad(dp[i+1][j-1], mul(dp[i][j], j-1));
                //new
                ad(dp[i+1][j+1], mul(dp[i][j], j-1+(i+1<cs)+(i+1<cf)));
            }
        }
    }
    cout << dp[n][1];
}

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