oj.uz

Submission #569103

# Submission time Handle Problem Language Result Execution time Memory
569103 2022-05-26T16:44:32 Z Redhood Kangaroo (CEOI16_kangaroo) C++14
100 / 100
 51 ms 304 KB 
#include<bits/stdc++.h>

#define fi first
#define se second
#define sz(x) (int)(x).size()
#define pb push_back

typedef long long ll;
typedef long double ld;

using namespace std;

#define all(x) (x).begin(), (x).end()
const int mod = (int)1e9 + 7;
const int N = 2001;
void md(int &a){
    if(a >= mod)
        a-=mod;
}
int binpow(int a , int b){
    if(b == 0)return 1;
    int ans = binpow(a , b >> 1);
    ans = (1ll * ans * ans) % mod;
    if(b & 1)
        ans = (1ll * ans * a) % mod;
    return ans;
}
int INV(int x){
    return binpow(x , mod - 2);
}
int dp[2][N];
signed main(){
    int n , a , b;
    cin >> n >> a >> b;

    int bt = 0;



    dp[bt][0] = 1;

    int inv = 1;
    for(int i = 0; i < n - 2; ++i)
        inv *= 2;
    inv = INV(inv);

    int met = 0;
    int inv2 = INV(2);
    for(int i = n; i >= 1; --i){
        /// okay so?
        bt ^= 1;
        fill(dp[bt] , dp[bt] + N , 0);
        if(i == a || i == b){
            for(int j = 0; j <= n-i;++j){
                /// either add or what
                dp[bt][j + 1] += dp[bt^1][j];
                md(dp[bt][j + 1]);
                int t = j - met;
                if(t >= 0){
                    dp[bt][j] += (1ll * dp[bt^1][j] * t % mod * 2 % mod);
                    md(dp[bt][j]);
                }
                if(i == 1){
                    dp[bt][j] += dp[bt^1][j];
                    md(dp[bt][j]);
                }
            }
            met++;
        }else{

            for(int j = 0; j <= n-i;++j){
                /// either add or what
                dp[bt][j + 1] += 1ll * dp[bt^1][j] * inv2 % mod;
                md(dp[bt][j + 1]);
                int t = j - met;
                if(t >= 0){
                    if(j >= 0)
                    dp[bt][j - 1] += (1ll * dp[bt^1][j] * t % mod * (t - 1) % mod * 2 % mod), md(dp[bt][j - 1]);
                    if(j >= 0)
                    dp[bt][j - 1] += (1ll * dp[bt^1][j] * t % mod * 2 % mod * met % mod), md(dp[bt][j - 1]);
                    if(i == 1){
                        dp[bt][j - 1] += dp[bt^1][j];
                        md(dp[bt][j-1]);
                    }
                }
            }
        }
//        cerr << " after " << i << '\n';
//        for(int x = 0; x <= n - i + 1; ++x)
//            cerr << dp[bt][x] << ' ';
//        cerr << '\n';
    }
    int ans = dp[bt][1];
    cout << ans;
    return 0;
}
/*
*/

Subtask #1
6.0 / 6.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 212 KB Output is correct
2 Correct 1 ms 212 KB Output is correct

Subtask #2
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 212 KB Output is correct
2 Correct 1 ms 212 KB Output is correct
3 Correct 0 ms 212 KB Output is correct
4 Correct 1 ms 212 KB Output is correct
5 Correct 1 ms 300 KB Output is correct
6 Correct 1 ms 212 KB Output is correct
7 Correct 1 ms 212 KB Output is correct
8 Correct 1 ms 212 KB Output is correct
9 Correct 1 ms 300 KB Output is correct
10 Correct 1 ms 304 KB Output is correct
11 Correct 1 ms 212 KB Output is correct

Subtask #3
15.0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 212 KB Output is correct
2 Correct 1 ms 212 KB Output is correct
3 Correct 0 ms 212 KB Output is correct
4 Correct 1 ms 212 KB Output is correct
5 Correct 1 ms 300 KB Output is correct
6 Correct 1 ms 212 KB Output is correct
7 Correct 1 ms 212 KB Output is correct
8 Correct 1 ms 212 KB Output is correct
9 Correct 1 ms 300 KB Output is correct
10 Correct 1 ms 304 KB Output is correct
11 Correct 1 ms 212 KB Output is correct
12 Correct 1 ms 280 KB Output is correct
13 Correct 1 ms 212 KB Output is correct
14 Correct 1 ms 212 KB Output is correct
15 Correct 1 ms 212 KB Output is correct
16 Correct 1 ms 212 KB Output is correct
17 Correct 1 ms 212 KB Output is correct
18 Correct 1 ms 212 KB Output is correct
19 Correct 1 ms 212 KB Output is correct
20 Correct 1 ms 212 KB Output is correct

Subtask #4
49.0 / 49.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 212 KB Output is correct
2 Correct 1 ms 212 KB Output is correct
3 Correct 0 ms 212 KB Output is correct
4 Correct 1 ms 212 KB Output is correct
5 Correct 1 ms 300 KB Output is correct
6 Correct 1 ms 212 KB Output is correct
7 Correct 1 ms 212 KB Output is correct
8 Correct 1 ms 212 KB Output is correct
9 Correct 1 ms 300 KB Output is correct
10 Correct 1 ms 304 KB Output is correct
11 Correct 1 ms 212 KB Output is correct
12 Correct 1 ms 280 KB Output is correct
13 Correct 1 ms 212 KB Output is correct
14 Correct 1 ms 212 KB Output is correct
15 Correct 1 ms 212 KB Output is correct
16 Correct 1 ms 212 KB Output is correct
17 Correct 1 ms 212 KB Output is correct
18 Correct 1 ms 212 KB Output is correct
19 Correct 1 ms 212 KB Output is correct
20 Correct 1 ms 212 KB Output is correct
21 Correct 6 ms 212 KB Output is correct
22 Correct 8 ms 304 KB Output is correct
23 Correct 9 ms 212 KB Output is correct
24 Correct 51 ms 212 KB Output is correct
25 Correct 45 ms 296 KB Output is correct
26 Correct 48 ms 296 KB Output is correct
27 Correct 44 ms 292 KB Output is correct
28 Correct 27 ms 304 KB Output is correct