Submission #1058956

#	Time	Username	Problem	Language	Result	Execution time	Memory
1058956		shenfe1	Ancient Books (IOI17_books)	C++17	100 / 100	238 ms	129112 KiB

books

#include <bits/stdc++.h>
#include "books.h"

#pragma GCC optimize("Ofast")

using namespace std;

#define pb push_back
#define pii pair<int,int>
#define sz(s) (int)s.size()
#define F first
#define S second
#define all(v) v.begin(),v.end()
#define ll long long
#define lb lower_bound

const int MAX=1e6+10;
const ll inf=1e18;

int n;
vector<int> g[MAX];
bool use[MAX];
vector<int> vec;
int pref[MAX];

struct dsu{
    int f[MAX];

    void init(int n){
        for(int i=0;i<n;i++)f[i]=i;
    }

    int get(int v){
        return (f[v]==v?v:f[v]=get(f[v]));
    }

    void unite(int a,int b){
        a=get(a),b=get(b);
        f[a]=b;
    }
}d;

int num[MAX];
int prefz[MAX];

bool is(int l,int r,vector<int> x){
    for(int pos:x){
        if(l<=pos&&pos<=r)return 1;
    }
    return 0;
}

int get(int l,int r){
    if(l==0)return prefz[r];
    return prefz[r]-prefz[l-1];
}

ll minimum_walk(vector<int> p,int s){
    n=sz(p);
    int Lneed=0,Rneed=n-1;
    ll ans=0;
    for(int i=0;i<n;i++){
        ans+=abs(i-p[i]);
    }
    vector<vector<int>> x;
    vector<pii> seg,bds;
    for(int i=0;i<n;i++){
        if(!use[i]){
            vec.clear();
            int v=i;
            while(!use[v]){
                num[v]=sz(seg);
                vec.pb(v);
                use[v]=1;
                v=p[v];
            }
            sort(all(vec));
            seg.pb({vec[0],vec.back()});
            int l=0,r=n-1;
            for(int f:vec){
                if(f<=s)l=f;
                else{
                    r=f;
                    break;
                }
            }
            bds.pb({l,r});
            x.pb(vec);
        }
    }
    d.init(n);
    vector<int> pref(n,0);
    for(int i=0;i<sz(seg);i++){
        auto &[l,r]=seg[i];
        if(l<=s&&s<=r&&i!=num[s]){
            continue;
        }
        pref[l]++;
        pref[r]--;
    }
    for(int i=1;i<n;i++)pref[i]+=pref[i-1];
    prefz[0]=(pref[0]==0);
    for(int i=1;i<n;i++){
        // if(pref[i]==0)cout<<i<<"\n";
        prefz[i]=prefz[i-1]+(pref[i]==0);
    }
    int cur=0;
    int L=s,R=s;
    set<pii> sl,sr;
    for(int i=0;i<sz(seg);i++){
        auto [l,r]=seg[i];
        if(l<s&&s<r&&i!=num[s]){
            // cout<<i<<"\n";
            // cout<<l<<" "<<r<<"\n";
            sl.insert({bds[i].F,i});
            sr.insert({bds[i].S,i});
        }
    }
    while(R-L+1!=n){
        while(L-1>=0&&pref[L-1]!=0)L--;
        while(R+1<n&&pref[R]!=0)R++;
        bool ok=0;
        // cout<<L<<" "<<R<<"\n";
        while(!sl.empty()&&L<=sl.rbegin()->F&&sl.rbegin()->F<=R){
            ok=1;
            int i=sl.rbegin()->S;
            sl.erase(--sl.end());
            sr.erase({bds[i].S,i});
            L=min(L,seg[i].F);
            R=max(R,seg[i].S);
        }
        while(!sr.empty()&&L<=sr.begin()->F&&sr.begin()->F<=R){
            ok=1;
            int i=sr.begin()->S;
            sr.erase(sr.begin());
            sl.erase({bds[i].F,i});
            L=min(L,seg[i].F);
            R=max(R,seg[i].S);
        }
        if(!ok){
            int mn=n+10,pos=-1;
            if(!sl.empty()){
                if(get(sl.rbegin()->F,L-1)<mn){
                    mn=get(sl.rbegin()->F,L-1);
                    pos=sl.rbegin()->S;
                }
            }
            if(!sr.empty()){
                if(get(R,sr.begin()->F-1)<mn){
                    mn=get(R,sr.begin()->F-1);
                    pos=sr.begin()->S;
                }
            }
            if(pos!=-1){
                ok=1;
                ans+=2*mn;
                L=seg[pos].F,R=seg[pos].S;
                sl.erase({bds[pos].F,pos});
                sr.erase({bds[pos].S,pos});
            }
        }
        while(L-1>=0&&pref[L-1]!=0)L--;
        while(R+1<n&&pref[R]!=0)R++;
        if(!ok){
            if(L-1>=0){
                L--;
                ans+=2;
            }
            if(R+1<n){
                R++;
                ans+=2;
            }
        }
    }
    for(int i=0;i<s;i++){
        if(p[i]==i)ans-=2;
        else break;
    }
    for(int i=n-1;i>s;i--){
        if(p[i]==i)ans-=2;
        else break;
    }

    return ans;
}

Compilation message (stderr)

books.cpp: In function 'long long int minimum_walk(std::vector<int>, int)':
books.cpp:60:9: warning: unused variable 'Lneed' [-Wunused-variable]
   60 |     int Lneed=0,Rneed=n-1;
      |         ^~~~~
books.cpp:60:17: warning: unused variable 'Rneed' [-Wunused-variable]
   60 |     int Lneed=0,Rneed=n-1;
      |                 ^~~~~
books.cpp:107:9: warning: unused variable 'cur' [-Wunused-variable]
  107 |     int cur=0;
      |         ^~~

• Subtask 1: 12 / 12
• Subtask 2: 10 / 10
• Subtask 3: 28 / 28
• Subtask 4: 20 / 20
• Subtask 5: 30 / 30