Submission #924880

#	Time	Username	Problem	Language	Result	Execution time	Memory
924880		Github	Kangaroo (CEOI16_kangaroo)	C++17	100 / 100	22 ms	31888 KiB

kangaroo

#include <iostream>
#include <vector>
#include <queue>
#include <cstring>
#include <map>
#include <climits>
#include <set>
#include <cmath>
#include <algorithm>
#include <stack>
using namespace std;

#define speedup ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
#define ll long long
const ll MOD = 1e9+7, MAXN = 5*1e6+5;



int main() {
    speedup
    int n, a, b; cin >> n >> a >> b;
    vector<vector<ll>> dp(n+1, vector<ll>(n+1));
    dp[1][1] = 1;
    for (int i = 2; i <= n; i++){
        for (int j = 1; j <= i; j++){
            if (i == a || i == b){
                dp[i][j] = (dp[i-1][j]+dp[i-1][j-1])%MOD;
            }else{
                dp[i][j] = (dp[i-1][j+1]*j+dp[i-1][j-1]*(max(j-(i>a)-(i>b), 0)))%MOD;
            }
        }
    }
    if (dp[n][1] < 0){
        dp[n][1] += MOD;
    }
    cout << dp[n][1] << endl;
    return 0;
}

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