Submission #283485

#	Time	Username	Problem	Language	Result	Execution time	Memory
283485		caoash	Kangaroo (CEOI16_kangaroo)	C++14	100 / 100	48 ms	31736 KiB

kangaroo

#include <bits/stdc++.h> 
using namespace std;

using ll = long long;

using vi = vector<int>;
#define pb push_back
#define rsz resize
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()

using pi = pair<int,int>;
#define f first
#define s second
#define mp make_pair

const int MOD = (int) 1e9 + 7;

ll dp[2005][2005];

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n, a, b; cin >> n >> a >> b;
    dp[0][0] = 1;
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= n; j++) {
            if (i == a || i == b) {
                dp[i][j] = dp[i - 1][j] + dp[i - 1][j - 1];
            }
            else {
                dp[i][j] = ((j * dp[i - 1][j + 1]) % MOD) + (((j - (i > a) - (i > b)) * dp[i - 1][j - 1]) % MOD) % MOD;
            }
        }
    }
    cout << dp[n][1] << '\n';
}

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