Submission #57079

#	Time	Username	Problem	Language	Result	Execution time	Memory
57079		Benq	Boat (APIO16_boat)	C++14	100 / 100	1316 ms	3820 KiB

boat

#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 = 100001;

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 ad(ll a, ll b) { return (a+b)%MOD; }
ll sub(ll a, ll b) { return (a-b+MOD)%MOD; }
ll mul(ll a, ll b) { return a*b%MOD; }
ll divi(ll a, ll b) { return mul(a,inv(b)); }

int N, dp[1000][501], in[1001];
vi rm;
map<int,int> m;
vpi v;

void input() {
    ios_base::sync_with_stdio(0); cin.tie(0);
    cin >> N;
    F0R(i,N) {
        int a,b; cin >> a >> b;
        v.pb({a,b});
        m[a-1] = m[b] = 0;
    }
    FOR(i,1,1001) in[i] = inv(i);
    int co = 0;
    for (auto& a: m) {
        rm.pb(a.f);
        a.s = co++;
    }
}

int main() {
    input();
    F0R(i,sz(v)) {
        auto a = v[i];
        int l = m[a.f-1]+1, r = m[a.s];
        
        int csum = 1;
        FOR(j,1,r+1) {
            int tmp = 0; F0R(k,i) tmp = ad(tmp,dp[j][k]);
            if (l <= j) {
                int w = rm[j]-rm[j-1];
                FORd(k,1,i+1) dp[j][k] = ad(dp[j][k],mul(dp[j][k-1],mul(w-k,in[k+1])));
                dp[j][0] = ad(dp[j][0],mul(w,csum));
            }
            csum = ad(csum,tmp);
        }
    }
    int ans = 0;
    FOR(i,1,sz(m)) F0R(j,sz(v)) ans = ad(ans,dp[i][j]);
    cout << ans;
}

/* Look for:
* the exact constraints (multiple sets are too slow for n=10^6 :( ) 
* special cases (n=1?)
* overflow (ll vs int?)
* array bounds
*/

• Subtask 1: 9 / 9
• Subtask 2: 22 / 22
• Subtask 3: 27 / 27
• Subtask 4: 42 / 42