oj.uz

Submission #48914

# Submission time Handle Problem Language Result Execution time Memory
48914 2018-05-19T21:52:59 Z Benq Kangaroo (CEOI16_kangaroo) C++14
51 / 100
 2000 ms 14636 KB 
#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>

using namespace std;
using namespace __gnu_pbds;
 
typedef long long ll;
typedef long double ld;
typedef complex<ld> cd;

typedef pair<int, int> pi;
typedef pair<ll,ll> pl;
typedef pair<ld,ld> pd;

typedef vector<int> vi;
typedef vector<ld> vd;
typedef vector<ll> vl;
typedef vector<pi> vpi;
typedef vector<pl> vpl;
typedef vector<cd> vcd;

template <class T> using Tree = tree<T, null_type, less<T>, rb_tree_tag,tree_order_statistics_node_update>;

#define FOR(i, a, b) for (int i=a; i<(b); i++)
#define F0R(i, a) for (int i=0; i<(a); i++)
#define FORd(i,a,b) for (int i = (b)-1; i >= a; i--)
#define F0Rd(i,a) for (int i = (a)-1; i >= 0; i--)

#define sz(x) (int)(x).size()
#define mp make_pair
#define pb push_back
#define f first
#define s second
#define lb lower_bound
#define ub upper_bound
#define all(x) x.begin(), x.end()

const int MOD = 1000000007;
const ll INF = 1e18;
const int MX = 2001;

template<int SZ> struct Combo {
    ll fac[SZ+1], ifac[SZ+1];
    
    Combo() {
        fac[0] = ifac[0] = 1;
    	FOR(i,1,SZ+1) {
    	    fac[i] = i*fac[i-1] % MOD;
    	    ifac[i] = inv(fac[i]);
    	}
    }
    
    ll po (ll b, ll p) { return !p?1:po(b*b%MOD,p/2)*(p&1?b:1)%MOD; }
    ll inv (ll b) { return po(b,MOD-2); }
    
    ll comb(ll a, ll b) {
        if (a < b || b < 0 || a < 0) return 0;
        ll tmp = fac[a]*ifac[b] % MOD;
        tmp = tmp*ifac[a-b] % MOD;
        return tmp;
    }
};

Combo<MX> Co;

int dp[MX][MX];

int ad(int x, int y) { return (x+y)%MOD; }
int mul(int x, int y) { return (ll)x*y%MOD; }

void gen() {
    dp[0][0] = 1;
    FOR(i,1,MX) {
        if (i % 2 == 1) {
            FOR(j,1,i+1) dp[i][j] = ad(dp[i][j-1],dp[i-1][j-1]);
        } else {
            FORd(j,1,i) dp[i][j] = ad(dp[i][j+1],dp[i-1][j]);
        }
    }
}

int main() {
    gen();
    ios_base::sync_with_stdio(0); cin.tie(0);
    int N, cs, cf; cin >> N >> cs >> cf;
    if (cs > cf) swap(cs,cf);
    if (cs == 1) {
        cout << dp[N-1][cf-1];
        return 0;
    }
    int a = cs-2, b = cf-cs-1, c = N-cf;
    //cout << a << " " << b << " " << c << "\n";
    int ans = 0;
    F0R(A,a+1) {
        int mula = Co.comb(a,A);
        F0R(B,b+1) {
            int mulb = mul(mula,Co.comb(b,B));
            F0R(C,c+1) {
                //cout << A << " " << B << " " << C << " " << dp[A+1+B+C][A+1] << " " << dp[a+b+c+1-A-B-C][a+b+1-A-B] << "\n";
                ans = ad(ans,mul(mul(dp[A+1+B+C][A+1],dp[a+b+c+1-A-B-C][a+b+1-A-B]),mul(mulb,Co.comb(c,C))));
            }
        }
        // A+1 on left, B+C on right 
        // a+b+1-A on left, c-C on right 
    }
    cout << ans;
}

// read the question correctly (is y a vowel? what are the exact constraints?)
// look out for SPECIAL CASES (n=1?) and overflow (ll vs int?)

Subtask #1
6.0 / 6.0

# Verdict Execution time Memory Grader output
1 Correct 28 ms 14328 KB Output is correct
2 Correct 28 ms 14328 KB Output is correct

Subtask #2
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 28 ms 14328 KB Output is correct
2 Correct 28 ms 14328 KB Output is correct
3 Correct 28 ms 14328 KB Output is correct
4 Correct 28 ms 14328 KB Output is correct
5 Correct 30 ms 14356 KB Output is correct
6 Correct 29 ms 14356 KB Output is correct
7 Correct 30 ms 14376 KB Output is correct
8 Correct 31 ms 14492 KB Output is correct
9 Correct 29 ms 14608 KB Output is correct
10 Correct 28 ms 14608 KB Output is correct
11 Correct 28 ms 14608 KB Output is correct

Subtask #3
15.0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 28 ms 14328 KB Output is correct
2 Correct 28 ms 14328 KB Output is correct
3 Correct 28 ms 14328 KB Output is correct
4 Correct 28 ms 14328 KB Output is correct
5 Correct 30 ms 14356 KB Output is correct
6 Correct 29 ms 14356 KB Output is correct
7 Correct 30 ms 14376 KB Output is correct
8 Correct 31 ms 14492 KB Output is correct
9 Correct 29 ms 14608 KB Output is correct
10 Correct 28 ms 14608 KB Output is correct
11 Correct 28 ms 14608 KB Output is correct
12 Correct 32 ms 14608 KB Output is correct
13 Correct 31 ms 14608 KB Output is correct
14 Correct 29 ms 14608 KB Output is correct
15 Correct 34 ms 14608 KB Output is correct
16 Correct 30 ms 14608 KB Output is correct
17 Correct 35 ms 14608 KB Output is correct
18 Correct 30 ms 14608 KB Output is correct
19 Correct 32 ms 14608 KB Output is correct
20 Correct 33 ms 14608 KB Output is correct

Subtask #4
0 / 49.0

# Verdict Execution time Memory Grader output
1 Correct 28 ms 14328 KB Output is correct
2 Correct 28 ms 14328 KB Output is correct
3 Correct 28 ms 14328 KB Output is correct
4 Correct 28 ms 14328 KB Output is correct
5 Correct 30 ms 14356 KB Output is correct
6 Correct 29 ms 14356 KB Output is correct
7 Correct 30 ms 14376 KB Output is correct
8 Correct 31 ms 14492 KB Output is correct
9 Correct 29 ms 14608 KB Output is correct
10 Correct 28 ms 14608 KB Output is correct
11 Correct 28 ms 14608 KB Output is correct
12 Correct 32 ms 14608 KB Output is correct
13 Correct 31 ms 14608 KB Output is correct
14 Correct 29 ms 14608 KB Output is correct
15 Correct 34 ms 14608 KB Output is correct
16 Correct 30 ms 14608 KB Output is correct
17 Correct 35 ms 14608 KB Output is correct
18 Correct 30 ms 14608 KB Output is correct
19 Correct 32 ms 14608 KB Output is correct
20 Correct 33 ms 14608 KB Output is correct
21 Correct 201 ms 14616 KB Output is correct
22 Correct 230 ms 14628 KB Output is correct
23 Correct 241 ms 14636 KB Output is correct
24 Execution timed out 2063 ms 14636 KB Time limit exceeded
25 Halted 0 ms 0 KB -