Submission #279997

#	Time	Username	Problem	Language	Result	Execution time	Memory
279997		eohomegrownapps	Roller Coaster Railroad (IOI16_railroad)	C++14	30 / 100	346 ms	57616 KiB

railroad

#include "railroad.h"
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

int INF = 1e9;

vector<vector<int>> adjlist;
vector<int> comind;
vector<bool> visited;

void dfs(int ind, int com){
    //cout<<ind<<' '<<com<<'\n';
    visited[ind]=true;
    comind[ind]=com;
    for (int i : adjlist[ind]){
        if (!visited[i]){
            dfs(i,com);
        }
    }
}

struct UFDS{
    vector<int> parent;
    int n;
    UFDS(int _n){
        n=_n;
        parent.resize(n);
        for (int i = 0; i<n; i++){
            parent[i]=i;
        }
    }

    int root(int x){
        if (x==parent[x]){return x;}
        return parent[x]=root(parent[x]);
    }

    void connect(int a, int b){
        int ra = root(a);
        int rb = root(b);
        if (ra!=rb){
            parent[ra]=rb;
        }
    }

    bool connected(int a, int b){
        return root(a)==root(b);
    }
};

long long plan_roller_coaster(std::vector<int> s, std::vector<int> t) {
    vector<int> ind2coord;
    for (int i : s){
        ind2coord.push_back(i);
    }
    for (int i : t){
        ind2coord.push_back(i);
    }
    ind2coord.push_back(INF);
    ind2coord.push_back(1);
    sort(ind2coord.begin(),ind2coord.end());
    ind2coord.erase(unique(ind2coord.begin(),ind2coord.end()),ind2coord.end());
    s.push_back(INF);
    t.push_back(1);
    int n = ind2coord.size();

    for (int i = 0; i<s.size(); i++){
        s[i]=lower_bound(ind2coord.begin(),ind2coord.end(),s[i])-ind2coord.begin();
        t[i]=lower_bound(ind2coord.begin(),ind2coord.end(),t[i])-ind2coord.begin();
    }
    //start at 1, end at 1
    
    int ans = 0;

    vector<int> edgedelta(n);
    for (int i = 0; i<s.size(); i++){
        edgedelta[s[i]]++;
        edgedelta[t[i]]--;
    }
    int curdelta = 0;
    for (int i = 0; i<n-1; i++){
        curdelta+=edgedelta[i];
        if (curdelta<0){
            //need to go ltr / speed up (fine)
            s.push_back(i);
            t.push_back(i+1);
        }
        if (curdelta>0){
            //need to go rtl / slow down (not fine)
            ans+=curdelta*(ind2coord[i+1]-ind2coord[i]);
            s.push_back(i+1);
            t.push_back(i);
        }
    }

    //make connected components
    adjlist.resize(n);
    visited.resize(n);
    comind.resize(n);
    for (int i = 0; i<s.size(); i++){
        adjlist[s[i]].push_back(t[i]);
    }
    int cptr = 0;
    for (int i = 0; i<n; i++){
        if (!visited[i]){
            dfs(i,cptr);
            cptr++;
        }
    }
    vector<pair<int,pair<int,int>>> edges;
    for (int i = 0; i<n-1; i++){
        if (comind[i]!=comind[i+1]){
            edges.push_back({ind2coord[i+1]-ind2coord[i],{comind[i],comind[i+1]}});
        }
    }
    sort(edges.begin(), edges.end());
    UFDS u(n);
    for (auto e : edges){
        // are these connected?
        if (u.connected(e.second.first, e.second.second)){
            continue;
        }
        ans+=e.first;
        u.connect(e.second.first, e.second.second);
    }
    return ans;
}

Compilation message (stderr)

railroad.cpp: In function 'long long int plan_roller_coaster(std::vector<int>, std::vector<int>)':
railroad.cpp:68:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   68 |     for (int i = 0; i<s.size(); i++){
      |                     ~^~~~~~~~~
railroad.cpp:77:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   77 |     for (int i = 0; i<s.size(); i++){
      |                     ~^~~~~~~~~
railroad.cpp:101:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  101 |     for (int i = 0; i<s.size(); i++){
      |                     ~^~~~~~~~~

• Subtask 1: 0 / 11
• Subtask 2: 0 / 23
• Subtask 3: 30 / 30
• Subtask 4: 0 / 36