Submission #536142

#	Time	Username	Problem	Language	Result	Execution time	Memory
536142		KoD	Roller Coaster Railroad (IOI16_railroad)	C++17	100 / 100	271 ms	18388 KiB

railroad

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

using ll = long long;

using std::vector;
using std::array;
using std::pair;
using std::tuple;

int dedup(vector<int>& v) {
    std::sort(v.begin(), v.end());
    v.erase(std::unique(v.begin(), v.end()), v.end());
    return v.size();
}

int lowb(const vector<int>& v, const int x) {
    return std::lower_bound(v.begin(), v.end(), x) - v.begin();
}

struct union_find {
    vector<int> par;
    explicit union_find(const int n) : par(n, -1) {}
    int find(const int u) {
        return par[u] < 0 ? u : par[u] = find(par[u]);
    }
    bool merge(int x, int y) {
        x = find(x), y = find(y);
        if (x == y) return false;
        if (par[x] > par[y]) std::swap(x, y);
        par[x] += par[y];
        par[y] = x;
        return true;
    }
};

ll plan_roller_coaster(vector<int> s, vector<int> t) {
    const int n = s.size();
    vector<int> cx;
    cx.reserve(2 * n + 2);
    cx.push_back(0);
    cx.push_back(1000000001);
    std::copy(s.begin(), s.end(), std::back_inserter(cx));
    std::copy(t.begin(), t.end(), std::back_inserter(cx));
    const int m = dedup(cx);
    vector<int> coeff(m);
    coeff[0] -= 1;
    coeff[m - 1] += 1;
    union_find dsu(m);
    for (int i = 0; i < n; ++i) {
        const int a = lowb(cx, s[i]);
        const int b = lowb(cx, t[i]);
        coeff[a] += 1;
        coeff[b] -= 1;
        dsu.merge(a, b);
    }
    ll cur = 0, ret = 0;
    vector<tuple<int, int, int>> edge;
    for (int i = 0; i < m; ++i) {
        if (i > 0) {
            if (cur != 0) dsu.merge(i - 1, i);
            if (cur > 0) ret += cur * (cx[i] - cx[i - 1]);
            edge.emplace_back(cx[i] - cx[i - 1], i - 1, i);
        } 
        cur += coeff[i];
    }
    std::sort(edge.begin(), edge.end());
    for (const auto& [c, u, v] : edge) {
        if (dsu.merge(u, v)) {
            ret += c;
        }
    }
    return ret;
}

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