Submission #124724

#	Time	Username	Problem	Language	Result	Execution time	Memory
124724		zubec	Roller Coaster Railroad (IOI16_railroad)	C++14	100 / 100	428 ms	40268 KiB

railroad

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

const int N = 400100;

vector <int> g[N];

bool used[N];

void dfs(int v){
    used[v] = 1;
    for (int i = 0; i < g[v].size(); i++){
        int to = g[v][i];
        if (!used[to])
            dfs(to);
    }
}

int dp[N], dsu[N], kol;

int dsu_get(int v){
    if (v == dsu[v])
        return v;
    return dsu[v] = dsu_get(dsu[v]);
}

void dsu_unite(int a, int b){
    a = dsu_get(a);
    b = dsu_get(b);
    if (a == b)
        return;
    dsu[b] = a;
    --kol;
}

long long plan_roller_coaster(std::vector<int> s, std::vector<int> t) {
    vector <int> zhat;
    s.push_back(1e9);
    t.push_back(1);
    for (int i = 0; i < s.size(); i++){
        zhat.push_back(s[i]);
        zhat.push_back(t[i]);
    }
    sort(zhat.begin(), zhat.end());
    zhat.erase(unique(zhat.begin(), zhat.end()), zhat.end());
    kol = zhat.size();
    for (int i = 0; i < zhat.size(); i++)
        dsu[i] = i;
    memset(dp, 0, sizeof(dp));
    for (int i = 0; i < s.size(); i++){
        int ss = lower_bound(zhat.begin(), zhat.end(), s[i])-zhat.begin();
        int tt = lower_bound(zhat.begin(), zhat.end(), t[i])-zhat.begin();
        --dp[ss];
        ++dp[tt];
        dsu_unite(ss, tt);
        g[ss].push_back(tt);
    }
    int cur = 0;
    ll ans = 0;
    vector <pair<int, int> > edges;
    for (int i = 0; i + 1 < zhat.size(); i++){
        cur += dp[i];
        if (cur > 0){
            g[i].push_back(i+1);
            dsu_unite(i, i+1);
        }
        if (cur < 0){
            g[i+1].push_back(i);
            ans -= cur*1ll*(zhat[i+1]-zhat[i]);
            dsu_unite(i+1, i);
        }
        edges.push_back({zhat[i+1]-zhat[i], i});
    }
    sort(edges.begin(), edges.end());
    for (int i = 0; i < edges.size(); i++){
        int len = edges[i].first, id = edges[i].second;
        int a = dsu_get(id), b = dsu_get(id+1);
        if (a == b)
            continue;
        dsu_unite(a, b);
        ans += len;
        if (kol == 1)
            break;
    }
    return ans;

}

Compilation message (stderr)

railroad.cpp: In function 'void dfs(int)':
railroad.cpp:15:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < g[v].size(); i++){
                     ~~^~~~~~~~~~~~~
railroad.cpp: In function 'long long int plan_roller_coaster(std::vector<int>, std::vector<int>)':
railroad.cpp:43:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < s.size(); i++){
                     ~~^~~~~~~~~~
railroad.cpp:50:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < zhat.size(); i++)
                     ~~^~~~~~~~~~~~~
railroad.cpp:53:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < s.size(); i++){
                     ~~^~~~~~~~~~
railroad.cpp:64:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i + 1 < zhat.size(); i++){
                     ~~~~~~^~~~~~~~~~~~~
railroad.cpp:78:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < edges.size(); i++){
                     ~~^~~~~~~~~~~~~~

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