Submission #975470

#	Time	Username	Problem	Language	Result	Execution time	Memory
975470		Kenjikrab	Boat (APIO16_boat)	C++14	58 / 100	2066 ms	8812 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;
}
vector<int> inverse(510);
void inv(int a)
{
    inverse[a]=pow(a,mod-2);
}
int invfac[1010];
int cycle=1;
int choose(int a,int b)
{
    if(b>a)return 0;
    if(a==b)return 1;
    if(a-b>b)b=a-b;
    int ret=1;
    if((b+1)/mod<a/mod)ret=0;
    else for(int i=b+1;i<=a;i++)
    {
        ret*=i;
        ret%=mod;
    }
    ret*=invfac[a-b];
    ret%=mod;
    return ret;
}

signed main()
{
    cin.tie(nullptr)->sync_with_stdio(false);
    for(int i=2;i<510;i++)inv(i);
    invfac[0]=1;
    invfac[1]=1;
    for(int i=2;i<510;i++)invfac[i]=invfac[i-1]*inverse[i],invfac[i]%=mod;
    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;
    }
    vector<vector<int>> pre(510,vector<int>(1010,-2));
    vector<int> latest(1010,-1);
    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 bef=latest[j];
            pre[i][j]=latest[j];
            latest[j]=i;
            int a=qr(j),b=(val[j+1]-val[j]),c=0;
            dp[i][j]=a;
            int ans=a*b;
            ans%=mod;
            int k=2;
            //cout<<i<<" "<<j<<" "<<ans<<" ";
            while(bef!=-1)
            {
                ans+=dp[bef][j]*choose(b+k-2,k);
                ans%=mod;
                bef=pre[bef][j];
                k++;
                //cout<<endl<<bef<<" "<<ans<<" ";
            }
           // cout<<endl;
            upd(j+1,ans);
        }
    }
    cout<<(qr(1007)+mod-1)%mod;
    return 0;
}

Compilation message (stderr)

boat.cpp: In function 'int main()':
boat.cpp:94:45: warning: unused variable 'c' [-Wunused-variable]
   94 |             int a=qr(j),b=(val[j+1]-val[j]),c=0;
      |                                             ^

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