Submission #906806

#	Time	Username	Problem	Language	Result	Execution time	Memory
906806		mathnetic	Roller Coaster Railroad (IOI16_railroad)	C++17	100 / 100	505 ms	33172 KiB

railroad

#include <cassert>
#include <cstdio>
#include <algorithm>
#include <unordered_map>
#include "railroad.h"

using namespace std;

typedef pair<int,int> ii;
typedef long long ll;

unordered_map<int, int> uf;

int fnd(int x){
    if(uf[x]==0) uf[x]=x;
    if(x==uf[x]) return x;
    else return uf[x]=fnd(uf[x]);
}
void un(int x, int y){
    uf[fnd(x)]=fnd(y);
}

bool cmp(ii a, ii b){
    return (a.second-a.first)<(b.second-b.first);
}


ll plan_roller_coaster(vector<int> s, vector<int> t){
    ll sol=0;
    s.push_back(1e9);
    t.push_back(1);
    int n = (int) s.size();
    vector<ii> e, ed;
    for(int i=0;i<n;++i){
        un(s[i], t[i]);
        e.emplace_back(s[i], 1);
        e.emplace_back(t[i], -1);
    }

    sort(e.begin(), e.end());
    int b=0;
    for(int i=0, j=0;i<e.size();i=j){
        for(;j<e.size() && e[j].first==e[i].first;++j){
           b+=e[j].second; 
        }
        if(j<e.size()){
            if(b>0){
                sol+=(ll)b*(e[j].first-e[i].first);
            }
            if(b==0){
                ed.emplace_back(e[i].first, e[j].first);
            }else{
                un(e[j].first, e[i].first);
            }
        }
    }
    sort(ed.begin(), ed.end(), cmp);
    for(auto i:ed){
        if(fnd(i.first)!=fnd(i.second)){
            sol+=i.second-i.first;
            un(i.first, i.second);
        }
    }
    return sol;
}

Compilation message (stderr)

railroad.cpp: In function 'll plan_roller_coaster(std::vector<int>, std::vector<int>)':
railroad.cpp:42:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   42 |     for(int i=0, j=0;i<e.size();i=j){
      |                      ~^~~~~~~~~
railroad.cpp:43:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   43 |         for(;j<e.size() && e[j].first==e[i].first;++j){
      |              ~^~~~~~~~~
railroad.cpp:46:13: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   46 |         if(j<e.size()){
      |            ~^~~~~~~~~

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