Submission #254600

#	Time	Username	Problem	Language	Result	Execution time	Memory
254600		MKopchev	Dancing Elephants (IOI11_elephants)	C++14	100 / 100	7532 ms	23964 KiB

elephants

#include "elephants.h"
#include <bits/stdc++.h>
using namespace std;

const int nmax=1.5e5+42;

int n,l,where[nmax];

set< pair<int/*position*/,int/*id*/> > active;

int BLOCK;

int which_block[nmax];

int IN=0;

vector< pair<int/*position*/,int/*id*/> > BLOCKS[nmax];

pair<int/*photos*/,int/*last from the same block*/> nxt[nmax];

pair<int/*position*/,int/*id*/> help[nmax];

int get_nxt(int who)
{
    /*
    cout<<"who= "<<who<<endl;
    cout<<"where: ";for(int i=0;i<n;i++)cout<<where[i]<<" ";cout<<endl;
    cout<<"active: ";for(auto k:active)cout<<k.first<<" "<<k.second<<"\t";cout<<endl;
    cout<<"nxt: ";for(int i=0;i<n;i++)cout<<nxt[i].first<<" "<<nxt[i].second<<"\t";cout<<endl;
    cout<<"BLOCKS: "<<endl;
    for(int i=0;i<(n-1)/BLOCK+1;i++)
    {
        cout<<i<<" -> ";for(auto k:BLOCKS[i])cout<<k.first<<" "<<k.second<<"\t";cout<<endl;
    }
    */
    int t=l+where[who];

    t++;

    set< pair<int/*position*/,int/*id*/> >::iterator it=active.lower_bound({t,0});

    if(it==active.end())return -1;

    return (*it).second;
}

void build_block(int which)
{
    //the last might be wrong

    int pointer=BLOCKS[which].size();

    if(pointer==0)return;

    pointer=pointer-2;

    while(pointer>=0&&BLOCKS[which][pointer].first>BLOCKS[which][pointer+1].first)
    {
        swap(BLOCKS[which][pointer],BLOCKS[which][pointer+1]);
        pointer--;
    }

    pointer=BLOCKS[which].size()-1;

    for(int i=BLOCKS[which].size()-1;i>=0;i--)
    {
        if(BLOCKS[which][i].first+l>=BLOCKS[which][BLOCKS[which].size()-1].first)nxt[BLOCKS[which][i].second]={0,BLOCKS[which][i].second};
        else
        {
            while(BLOCKS[which][i].first+l<BLOCKS[which][pointer-1].first)pointer--;

            int moved=BLOCKS[which][pointer].second;

            nxt[BLOCKS[which][i].second]={nxt[moved].first+1,nxt[moved].second};
        }
    }
    /*
    cout<<"building "<<which<<endl;
    for(auto k:BLOCKS[which])cout<<k.first<<" "<<k.second<<"\t";cout<<endl;
    for(int i=0;i<given.size();i++)cout<<nxt[given[i].second].first<<" "<<nxt[given[i].second].second<<"\t";cout<<endl;
    system("pause");
    */
}

void build()
{
    for(int i=0;i<n;i++)
        help[i]={where[i],i};

    sort(help,help+n);

    int total=(n-1)/BLOCK+1;

    for(int i=0;i<total;i++)BLOCKS[i]={};

    for(int i=0;i<n;i++)
    {
        BLOCKS[i/BLOCK].push_back({help[i].first,help[i].second});
        which_block[help[i].second]=i/BLOCK;
    }

    for(int i=0;i<total;i++)
    {
        sort(BLOCKS[i].begin(),BLOCKS[i].end());
        build_block(i);
    }
}

void init(int N,int L,int X[])
{
    n=N;
    l=L;
    for(int i=0;i<N;i++)
    {
        where[i]=X[i];
        active.insert({where[i],i});
    }

    BLOCK=sqrt(n*log(n))+1;
    build();
}


int update(int id,int val)
{
    //cout<<"UPDATE "<<id<<" "<<val<<endl;

    if(n==1)return 1;

    active.erase({where[id],id});

    for(int i=0;true;i++)
        if(BLOCKS[which_block[id]][i]==make_pair(where[id],id))
        {
            BLOCKS[which_block[id]].erase(BLOCKS[which_block[id]].begin()+i);
            break;
        }

    build_block(which_block[id]);

    where[id]=val;

    set< pair<int/*position*/,int/*id*/> >::iterator it=active.lower_bound({where[id],id});
    if(it==active.end())it--;

    int new_block=which_block[(*it).second];

    which_block[id]=new_block;

    active.insert({where[id],id});
    BLOCKS[which_block[id]].push_back({where[id],id});

    build_block(which_block[id]);

    if(BLOCKS[which_block[id]].size()>2*BLOCK)build();

    int ret=0,who=(*active.begin()).second;

    while(who!=-1)
    {
        ret+=nxt[who].first;

        who=nxt[who].second;

        ret++;

        who=get_nxt(who);
    }

    return ret;
}

/*
int N_,L_,X_[nmax];
int main()
{
    cin>>N_>>L_;
    for(int i=0;i<N_;i++)cin>>X_[i];

    init(N_,L_,X_);

    int q;
    cin>>q;

    for(int i=1;i<=q;i++)
    {
        int pos,val;
        cin>>pos>>val;

        cout<<update(pos,val)<<endl;
    }


    cout<<update(0,10)<<endl;

    cout<<update(5,11)<<endl;

    cout<<update(7,12)<<endl;

    cout<<update(8,13)<<endl;

    cout<<update(4,14)<<endl;

    cout<<update(6,15)<<endl;
    return 0;
}
*/

Compilation message (stderr)

elephants.cpp: In function 'int update(int, int)':
elephants.cpp:155:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     if(BLOCKS[which_block[id]].size()>2*BLOCK)build();
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 16 / 16
• Subtask 3: 24 / 24
• Subtask 4: 47 / 47
• Subtask 5: 3 / 3