Submission #642477

#	Time	Username	Problem	Language	Result	Execution time	Memory
642477		BackNoob	Kangaroo (CEOI16_kangaroo)	C++14	100 / 100	31 ms	15964 KiB

kangaroo

#include <bits/stdc++.h>
#define ll long long
#define fi first
#define se second
#define endl '\n'
#define MASK(i) (1LL << (i))
#define ull unsigned long long
#define ld long double
#define pb push_back
#define all(x) (x).begin() , (x).end()
#define BIT(x , i) ((x >> (i)) & 1)
#define TASK "task"
#define sz(s) (int) (s).size()
 
using namespace std;
const int mxN = 2008;
const int inf = 1e9 + 277;
const int mod = 1e9 + 7;
const ll infll = 1e18 + 7;
const int base = 307;
const int LOG = 20;
 
template <typename T1, typename T2> bool minimize(T1 &a, T2 b) {
    if (a > b) {a = b; return true;} return false;
}
template <typename T1, typename T2> bool maximize(T1 &a, T2 b) {
    if (a < b) {a = b; return true;} return false;
}

int n;
int sta;
int fin;
int dp[mxN][mxN];

void add(int &a, int b)
{
    a += b;
    if(a >= mod)
        a -= mod;
}

void solve()
{
    cin >> n >> sta >> fin;
    dp[1][1] = 1;

    for(int i = 2; i <= n; i++) {
        for(int j = 1; j <= n; j++) {
            if(i == sta || i == fin) {
                add(dp[i][j], dp[i - 1][j - 1]);
                add(dp[i][j], dp[i - 1][j]);
            }
            else {
                add(dp[i][j], 1LL * dp[i - 1][j + 1] * j % mod);
                add(dp[i][j], 1LL * dp[i - 1][j - 1] * (j - (i > sta) - (i > fin)) % mod);
            }
        }
    }

    cout << dp[n][1];
}
 
int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);

 
    int tc = 1;
    //cin >> tc;
    while(tc--) {
        solve();
    }
    return 0;
}

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