Submission #292512

#	Time	Username	Problem	Language	Result	Execution time	Memory
292512		Aldas25	Roller Coaster Railroad (IOI16_railroad)	C++14	100 / 100	1251 ms	75176 KiB

railroad

#include "railroad.h"
#include <bits/stdc++.h>

using namespace std;

#define FOR(i, a, b) for (int i = (a); i <= (b); i++)
#define REP(n) FOR(O, 1, (n))
#define f first
#define s second
#define pb push_back
typedef vector<int> vi;
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<pii> vii;

const int MAXN = 1000100;
const ll INF = 1e16;

int pref[MAXN];
int par[MAXN];
ll balance[MAXN];
int find (int a) {return par[a] = par[a]==a ? a : find(par[a]);}
bool same (int a, int b) {return find(a) == find(b);}
void unite (int a, int b) {
    a = find(a), b = find(b);
    if (a == b) return;
    par[b] = a;
}

long long plan_roller_coaster(std::vector<int> s, std::vector<int> t) {
    int n = (int) s.size();

    s.pb((int)1000 * 1000 * 1000);
    t.pb(1);

    set<int> cur;
    map<int, int> toId, toCoords;
    FOR(i, 0, n) cur.insert(s[i]);
    FOR(i, 0, n) cur.insert(t[i]);

    int curId = 0;
    for (int x : cur) {
        toId[x] = ++curId;
        toCoords[curId] = x;
    }

    FOR(i, 0, curId+5) par[i] = i;

    FOR(i, 0, n) s[i] = toId[s[i]];
    FOR(i, 0, n) t[i] = toId[t[i]];

    //FOR(i, 0, n) cout << " i = " << i << " s[i] = " << s[i] << "  t[i] = " << t[i] << endl;

    FOR(i, 0, n) pref[s[i]]++, pref[t[i]]--;
   // FOR(i, 1, curId) cout <<"  i = "  << i<< " pref: " << pref[i] << endl;

    int ss = 0;
    FOR(i, 1, curId-1) {
        ss += pref[i];
        balance[i] = ss;
       // cout << " i = " << i << "  balance: " << balance[i] << endl;
    }

    FOR(i, 0, n) unite(s[i], t[i]);
    ll sum = 0ll;
    FOR(i, 1, curId-1) {
        if (balance[i] > 0) {
            unite(i, i+1);
            sum += balance[i] * (toCoords[i+1] - toCoords[i]);
        }
        if (balance[i] < 0) unite(i, i+1);
    }

    vector<pair<ll, pii>> edges;

    FOR(i, 1, curId-1) {
        if (!same(i, i+1)) {
            edges.pb({(toCoords[i+1] - toCoords[i]), {i, i+1}});
        }
    }

    sort(edges.begin(), edges.end());
    for (auto e : edges) {
        ll w = e.f;
        int u = e.s.f, v = e.s.s;
        if (!same (u,v)) {
            sum += w;
            unite(u,v);
        }
    }

    return sum;

}

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