Submission #849729

#	Time	Username	Problem	Language	Result	Execution time	Memory
849729		justinlgl20	Kangaroo (CEOI16_kangaroo)	C++14	100 / 100	17 ms	31832 KiB

kangaroo

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

#define int long long

int dp[2005][2005];
const int MOD = 1000000007;

int32_t main() {
        int n, start, end;
        cin >> n >> start >> end;
        dp[1][1] = 1;
        for (int i = 1; i <= n; i++) {
                for (int j = 1; j <= n; j++) {
                        if (i == 1 and j == 1) dp[i][j] = 1;
                        else if (i == 1) {dp[i][j] = 0; continue;}
                        else if (i != start and i != end) {
                                dp[i][j] = (int)(dp[i-1][j+1]*j)%MOD;
                                int k = j;
                                if (i > start) k -= 1;
                                if (i > end) k -= 1;
                                dp[i][j] += (int)(dp[i-1][j-1] * k)%MOD;
                        }
                        else {
                                dp[i][j] = dp[i-1][j-1];
                                dp[i][j]%=MOD;
                                dp[i][j] += dp[i-1][j];
                                dp[i][j]%=MOD;
                        }
                }
        }
        cout << dp[n][1] << "\n";
}

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