Submission #1058717

#	Time	Username	Problem	Language	Result	Execution time	Memory
1058717		shenfe1	Ancient Books (IOI17_books)	C++17	22 / 100	2041 ms	105544 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

const int MAX=1e6+10;

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];

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;
    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()});
            x.pb(vec);
        }
    }
    d.init(n);
    for(int i=0;i<sz(seg);i++){
        auto [l,r]=seg[i];
        for(int j=i+1;j<sz(seg);j++){
            for(int pos:x[j]){
                if(l<=pos&&pos<=r){
                    d.unite(i,j);
                }
            }
        }
    }
    for(int i=0;i<n-1;i++){
        if(d.get(num[i])!=d.get(num[i+1])){
            ans+=2;
            d.unite(num[i],num[i+1]);
        }
    }
    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:45:9: warning: unused variable 'Lneed' [-Wunused-variable]
   45 |     int Lneed=0,Rneed=n-1;
      |         ^~~~~
books.cpp:45:17: warning: unused variable 'Rneed' [-Wunused-variable]
   45 |     int Lneed=0,Rneed=n-1;
      |                 ^~~~~

• Subtask 1: 12 / 12
• Subtask 2: 10 / 10
• Subtask 3: 0 / 28
• Subtask 4: 0 / 20
• Subtask 5: 0 / 30