Submission #1005210

#	Time	Username	Problem	Language	Result	Execution time	Memory
1005210		milisav	Kangaroo (CEOI16_kangaroo)	C++14	100 / 100	10 ms	16220 KiB

kangaroo

#include <bits/stdc++.h>
#define maxn 2024
using namespace std;
const int mod = 1000000007;
int n, cs, cf;
int dp[maxn][maxn];
int main() {
    cin.tie(0); ios_base::sync_with_stdio(false);
    cin>>n>>cs>>cf;
    if(n==2) {
        cout<<1<<endl;
        return 0;
    }
    if(cf==1 || cs==1) dp[1][0]=1;
    else dp[1][1] = 1;
    for(int i=2;i<=n;i++) {
        for(long long g=0;g<=i;g++) {
            if(i<cs && i<cf) {
                dp[i][g] = ((g?dp[i-1][g-1]:0) + g*(g+1)*dp[i-1][g+1])%mod;
                continue;
            }
            if(i==cs || i==cf) {
                dp[i][g] = (dp[i-1][g] + (g+1)*dp[i-1][g+1])%mod;
                continue;
            }
            if(i>cf && i>cs) {
                dp[i][g] = ((g?dp[i-1][g-1]:0) + (g+2)*(g+1)*dp[i-1][g+1])%mod;
                continue;
            }
            else {
                dp[i][g] = ((g?dp[i-1][g-1]:0) + (g+1)*(g+1)*dp[i-1][g+1])%mod;
                continue;
            }
        }
    }
    cout<<dp[n-1][0]<<endl;
    return 0;
}

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