Submission #592926

#	Time	Username	Problem	Language	Result	Execution time	Memory
592926		Tudy006	Kangaroo (CEOI16_kangaroo)	C++14	100 / 100	25 ms	15964 KiB

kangaroo

#include <bits/stdc++.h>

using namespace std;

const int NMAX = 2000;
const int MOD = 1e9 + 7;

int dp[NMAX + 1][NMAX + 2];

int main() {
    int n, start, finish;
    cin >> n >> start >> finish;
    dp[0][1] = 1;
    for ( int i = 0; i < n; i ++ ) {
        for ( int j = 0; j <= n; j ++ ) {
            if ( i + 1 == start || i + 1 == finish ) {
                dp[i + 1][j] = ( dp[i + 1][j] + dp[i][j] ) % MOD;
                if ( j >= 1 ) dp[i + 1][j - 1] = ( dp[i + 1][j - 1] + dp[i][j] ) % MOD;
            } else {
                dp[i + 1][j + 1] = ( dp[i + 1][j + 1] + (long long)dp[i][j] * j ) % MOD;
                if ( j >= 1 ) dp[i + 1][j - 1] = ( dp[i + 1][j - 1] + (long long)dp[i][j] * ( j - ( i + 1 < start ) - ( i + 1 < finish ) ) ) % MOD;
            }
        }
    }
    cout << dp[n][0];
    return 0;
}

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