Submission #920553

#	Time	Username	Problem	Language	Result	Execution time	Memory
920553		irmuun	Boat (APIO16_boat)	C++17	27 / 100	2035 ms	8284 KiB

boat

#include<bits/stdc++.h>
 
using namespace std;
 
#define ll long long
#define pb push_back
#define ff first
#define ss second
#define all(s) s.begin(),s.end()
#define rall(s) s.rbegin(),s.rend()

const ll mod=1e9+7,N=1e3+5;

ll binpow(ll a,ll b){
    ll res=1;
    while(b){
        if(b&1){
            res=res*a%mod;
        }
        a=a*a%mod;
        b=b>>1;
    }
    return res;
}
ll inv(ll a){
    return binpow(a,mod-2);
}

ll fact[N],invfact[N];

void init(){
    fact[0]=1;
    for(ll i=1;i<N;i++){
        fact[i]=fact[i-1]*i%mod;
    }
    invfact[N-1]=inv(fact[N-1]);
    for(ll i=N-1;i>=1;i--){
        invfact[i-1]=invfact[i]*i%mod;
    }
}
ll nCk(ll n,ll k){
    if(k>n||k<0) return 0ll;
    ll res=1;
    for(ll i=n-k+1;i<=n;i++) res=res*i%mod;
    res=res*invfact[k]%mod;
    return res;
}

int main(){
    ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
    init();
    ll n;
    cin>>n;
    ll a[n+5],b[n+5];
    set<ll>s;
    for(ll i=1;i<=n;i++){
        cin>>a[i]>>b[i];
        s.insert(a[i]);
        s.insert(b[i]+1);
    }
    ll cur=0;
    ll l[2*n+5];
    for(auto x:s){
        cur++;
        l[cur]=x;
    }
    ll dp[2*n+5][n+5],sum[2*n+5][n+5];
    memset(sum,0,sizeof sum);
    ll ans=0;
    for(ll i=1;i<=n;i++){
        ll tot=1;
        memset(dp,0,sizeof dp);
        for(ll j=1;j<cur;j++){//l[j] l[j+1]-1
            if(b[i]>=l[j]&&a[i]<l[j+1]){
                dp[j][1]=tot;
                for(ll k=2;k<=n;k++){
                    dp[j][k]=sum[j][k-1];
                }
            }
            for(ll k=1;k<=n;k++){
                tot+=sum[j][k]*nCk(l[j+1]-l[j],k)%mod;
                tot%=mod;
            }
            for(ll k=1;k<=n;k++){
                sum[j][k]+=dp[j][k];
                sum[j][k]%=mod;
            }
        }
    }
    for(ll j=1;j<cur;j++){
        for(ll k=1;k<=n;k++){
            ans+=sum[j][k]*nCk(l[j+1]-l[j],k)%mod;
            ans%=mod;
        }
    }
    cout<<ans;
}

• Subtask 1: 0 / 9
• Subtask 2: 0 / 22
• Subtask 3: 27 / 27
• Subtask 4: 0 / 42