Submission #1168776

#	Time	Username	Problem	Language	Result	Execution time	Memory
1168776		spycoderyt	Kangaroo (CEOI16_kangaroo)	C++20	0 / 100	0 ms	392 KiB

kangaroo

#include <bits/stdc++.h>
#define int long long 
using namespace std;
const int N = 2005;
int dp[N][N];
const int mod = 1e9+7;
void add(int &a,int b){
    a = (a + b) % mod;
}
int32_t main() {
    int n,st,en,diff=0;
    cin >> n >> st >> en;
    dp[1][1]=1;
    if(st == 1 || en == 1) diff++;
    for(int i = 1;i<=n;i++) {
        for(int j = 1;j<=i;j++) {
            if(i == st || i == en) {
                // add new 
                if(i==1)continue;
                add(dp[i+1][j+1],dp[i][j]);
                // add to existing cmp
                add(dp[i+1][j], dp[i][j]);
                diff++;
            } else {
                // new cmp (use 3)
                if(i+1!=st&&i+1!=en&&i+2!=st&&i+2!=en){
                    add(dp[i+3][j+1], dp[i][j] * 2 * (j - diff + 1));
                }
                // add to cmp
                add(dp[i+1][j], dp[i][j] * (j - diff) * 2);
                // merge cmp
                if(j-1>=1)add(dp[i+1][j-1], dp[i][j] * (j-1));
            }
            // cerr << dp[i][j] << " ";
        }
        // cerr<<"\n";
    }
    cout << dp[n][1];
}
/*
no 3 can be increasing 2x or decreasing 2x

want to use the same update so force structure into the problme

*/

• Subtask 1: 0 / 6
• Subtask 2: 0 / 30
• Subtask 3: 0 / 15
• Subtask 4: 0 / 49