Submission #920565

#	Time	Username	Problem	Language	Result	Execution time	Memory
920565		irmuun	Boat (APIO16_boat)	C++17	27 / 100	26 ms	4696 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=5e2+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],C[N][N];

vector<ll>v;

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;
    }
    for(ll i=0;i<v.size();i++){
        ll cur=1,L=1,R=v[i];
        for(ll j=1;j<N;j++){
            if(j>v[i]){
                cur=0;
            }
            else{
                cur=cur*R%mod*inv(L)%mod;
                R--;
                L++;
            }
            C[i+1][j]=cur;
        }
    }
}
ll nCk(ll i,ll k){
    return C[i][k];
}

int main(){
    ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
    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;
    }
    for(ll i=1;i<cur;i++){
        v.pb(l[i+1]-l[i]);
    }
    init();
    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(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(j,k)%mod;
            ans%=mod;
        }
    }
    cout<<ans;
}

Compilation message (stderr)

boat.cpp: In function 'void init()':
boat.cpp:42:17: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   42 |     for(ll i=0;i<v.size();i++){
      |                ~^~~~~~~~~

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