Submission #974925

#	Time	Username	Problem	Language	Result	Execution time	Memory
974925		Kenjikrab	Boat (APIO16_boat)	C++14	9 / 100	2067 ms	190288 KiB

boat

#include<bits/stdc++.h>
#define int long long
#define pii pair<int,int>
#define fi first
#define se second
using namespace std;
int const mod=1e9+7;
map<int,int> ind;
vector<int> val;
vector<int> fen(1010,0);
void upd(int idx,int val)
{
    idx+=2;
    for(int i=idx;i<1010;i+=i&-i)fen[i]+=val,fen[i]%=mod;
}
int qr(int idx)
{
    idx+=2;
    int ret=0;
    for(int i=idx;i>0;i-=i&-i)ret+=fen[i],ret%=mod;
    return ret;
}
int pow(int a,int b)
{
    if(b==0)return 1;
    if(b==1)return a;
    int ret=pow(a,b/2);
    if(b%2==0)return (ret*ret)%mod;
    else return (((ret*ret)%mod)*a)%mod;
}
map<int,int> inverse;
int inv(int a)
{
    if(inverse[a]!=0)return inverse[a];
    inverse[a]=pow(a,mod-2);
    return inverse[a];
}

map<pii,int> chos;
int choose(int a,int b)
{
    if(b>a)return 0;
    int ret=1;
    if(chos[{a,b}]!=0)return chos[{a,b}];
    for(int i=b+1;i<=a;i++)
    {
        ret*=i;
        ret%=mod;
    }
    for(int i=2;i<=a-b;i++)
    {
        ret*=inv(i);
        ret%=mod;
    }
    chos[{a,b}]=ret;
    return ret;
}
signed main()
{
    int n;
    cin>>n;
    vector<pii> info;
    set<int> temp;
    for(int i=0;i<n;i++)
    {
        int a,b;
        cin>>a>>b;
        temp.insert(a);
        temp.insert(b+1);
        info.push_back({a,b+1});
    }
    for(auto it:temp)
    {
        val.push_back(it);
        ind[it]=val.size()-1;
        //cout<<it<<" "<<ind[it]<<endl;
    }
    vector<vector<int>> pre(510,vector<int>(1010,-2));
    vector<int> latest(1010,-1);
    for(int i=0;i<n;i++)
    {
        for(int j=ind[info[i].fi];j<ind[info[i].se];j++)
        {
            pre[i][j]=latest[j];
            latest[j]=i;
        }
    }
    upd(-1,1);
    vector<vector<int>> dp(510,vector<int>(1010,0));
    for(int i=0;i<n;i++)
    {
        //cout<<endl<<i<<":";
        for(int j=ind[info[i].se]-1;j>=ind[info[i].fi];j--)
        {
            //cout<<j<<" ";
            int a=qr(j),b=(val[j+1]-val[j]);
            dp[i][j]=a;
            int ans=a*b;
            ans%=mod;
            int bef=pre[i][j],k=2;
            //cout<<i<<" "<<j<<" "<<ans<<" ";
            while(bef!=-1)
            {
                int sum=0;
                for(int l=k;l>=2;l--)sum+=choose(b,l)*choose(k-2,l-2),sum%=mod;
                ans+=dp[bef][j]*sum;
                ans%=mod;
                bef=pre[bef][j];
                k++;
                //cout<<ans<<" ";
            }
            upd(j+1,ans);
            //cout<<endl;
        }
    }
    cout<<(qr(1007)+mod-1)%mod;
    return 0;
}

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