Submission #1092730

#	Time	Username	Problem	Language	Result	Execution time	Memory
1092730		alexander707070	Boat (APIO16_boat)	C++14	0 / 100	5 ms	4444 KiB

boat

#include<bits/stdc++.h>
#pragma GCC optimize ("O3")
#pragma GCC target ("sse4")

#define MAXN 507
using namespace std;

struct group{
    int from,to;
}s[2*MAXN];

const long long mod=1e9+7;

int n,a[MAXN],b[MAXN],m;
vector<int> pos;

bool in(group g,int id){
    return g.from>=a[id] and g.to<=b[id];
}

long long dp[MAXN][MAXN][2];
long long invfact[MAXN];

long long comb(int x,int g){

    long long res=1,sz=s[g].to-s[g].from+1;

    for(long long i=sz;i>=sz-x+1;i--){
        res*=i; res%=mod;
    }

    res*=invfact[x]; res%=mod;
    return res;
}

long long power(long long a,int b){
    if(b==0)return 1;
    if(b==1)return a;
    if(b==2)return (a*a)%mod;
    if(b%2==0)return power(power(a,b/2),2);
    return (a*power(power(a,b/2),2));
}

int main(){

    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    cin>>n;
    for(int i=1;i<=n;i++){
        cin>>a[i]>>b[i];
        pos.push_back(a[i]);
        pos.push_back(b[i]);
    }

    invfact[0]=1;
    for(int i=1;i<=n;i++){
        invfact[i]=(invfact[i-1]*i)%mod;
    }

    for(int i=1;i<=n;i++){
        invfact[i]=power(invfact[i],mod-2);
    }

    sort(pos.begin(),pos.end());
    for(int i=0;i<pos.size()-1;i++){
        if(pos[i]!=pos[i+1]){
            m++; s[m]={pos[i],pos[i]};
            
            if(pos[i]+1<=pos[i+1]-1){
                m++; s[m]={pos[i]+1,pos[i+1]-1};
            }
        }
    }

    m++;
    s[m]={pos.back(),pos.back()};

    dp[0][0][1]=dp[0][1][0]=dp[0][1][1]=1;

    for(int i=1;i<=n;i++){
        for(int f=1;f<=m;f++){
            for(int t=0;t<2;t++){
                
                dp[i][f][t]=dp[i-1][f][0];
                if(t==1)dp[i][f][t]+=dp[i][f-1][1];

                for(int k=i;k>=1 and i-k+1<=s[f].to-s[f].from+1;k--){
                    if(!in(s[f],k))break;

                    dp[i][f][t]+=(dp[k-1][f-1][1]*comb(i-k+1,f))%mod;
                }

                dp[i][f][t]%=mod;
            }
        }
    }

    cout<<dp[2][3][1]-1<<"\n";
 
    return 0;
}

Compilation message (stderr)

boat.cpp: In function 'int main()':
boat.cpp:67:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   67 |     for(int i=0;i<pos.size()-1;i++){
      |                 ~^~~~~~~~~~~~~

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