Submission #578461

#	Time	Username	Problem	Language	Result	Execution time	Memory
578461		definitelynotmee	Ancient Books (IOI17_books)	C++98	50 / 100	416 ms	104740 KiB

books

#include<bits/stdc++.h>
#include "books.h"
using namespace std;
#define ff first
#define ss second
#define all(x) x.begin(), x.end()
using ll = long long;
using pii = pair<int,int>;
using pll = pair<ll,ll>;
template<typename T>
using matrix = vector<vector<T>>;
const int INF = 1e9;
long long minimum_walk(std::vector<int> p, int s) {
    int n = p.size();
    ll resp =0;

    for(int i = 0; i < n; i++){
        resp+=abs(i-p[i]);
    }
    vector<pii> crange(n);
    vector<int> cycle(n), check(n);
    auto dfs = [&](int id, int cid, auto dfs)->int{
        cycle[id] = cid;
        check[id] = 1;
        if(check[p[id]])
            return id;
        return max(id,dfs(p[id],cid,dfs));
    };
    vector<int> isgood(n);
    vector<pii> cycles;
    
    for(int i = 0; i < n; i++){
        if(!check[i]){
            int r = dfs(i,i,dfs);
            crange[i] = {i,r};
            isgood[i] = cycles.empty() || cycles.back().ss < r;
            if(r-i && isgood[i]){
                if(cycles.size() && cycles.back().ss > i){
                    int l = cycles.back().ff;
                    cycles.pop_back();
                    cycles.push_back({l,r});
                } else {
                    cycles.push_back({i,r});
                }
            }
        }
    }
    
    for(int i = 0; i < (int)cycles.size()-1; i++){
        resp+= 2*(cycles[i+1].ff-cycles[i].ss);
    }
    if(cycles.empty())
        return resp;
    if(s < cycles[0].ff || s > cycles.back().ss){
        resp+=max(cycles[0].ff-s, s-cycles.back().ss)*2;
        return resp;
    }
    
    matrix<pii> g(n);
    for(int i = 0; i < n-1; i++){
        int cur = cycle[i];
        g[cur].push_back({cycle[i+1],2});
        g[cycle[i+1]].push_back({cur,2});
    }
    vector<int> st;
    for(int i = 0; i < n; i++){
        if(st.empty()){
            st.push_back(i);
            goto END;
        }
        g[st.back()].push_back({cycle[i],0});
        if(cycle[i]!=i)
            goto END;
        if(crange[st.back()].ss < crange[i].ss)
            st.pop_back();
        st.push_back(i);

        END:
        if(i == crange[st.back()].ss)
            st.pop_back();
    }

    priority_queue<pii,vector<pii>,greater<pii>> pq;
    vector<int> dist(n,INF);
    pq.push({0,cycle[s]});
    dist[cycle[s]] = 0;

    while(!pq.empty()){
        int cur = pq.top().ss, curp = pq.top().ff;
        pq.pop();
        if(curp> dist[cur])
            continue;
        for(auto [viz,vizp] : g[cur]){
            if(dist[viz] > vizp+dist[cur]){
                dist[viz]= vizp+dist[cur];
                pq.push({dist[viz],viz});
            }
        }
    }
    
    int add = INF;
    for(int i = 0; i < n; i++){
        if(isgood[i])
            add = min(add,dist[i]);
    }
    resp+=add;

    return resp;
}

Compilation message (stderr)

books.cpp: In function 'long long int minimum_walk(std::vector<int>, int)':
books.cpp:93:18: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   93 |         for(auto [viz,vizp] : g[cur]){
      |                  ^

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