Submission #1138196

#	Time	Username	Problem	Language	Result	Execution time	Memory
1138196		gyg	Roller Coaster Railroad (IOI16_railroad)	C++20	100 / 100	844 ms	98564 KiB

railroad

#include <bits/stdc++.h>
using namespace std;
#define int long long
#define arr array 
#define vec vector
#define pii pair<int, int> 
#define fir first 
#define sec second
#define hmap unordered_map
const int N = 2e5 + 5, INF = 2e9;

int n;
arr<int, N> s, t;

map<int, int> flw;
vec<pii> mrgd;
int flw_cmp() {
    for (int i = 0; i <= n; i++) {
        if (s[i] <= t[i])
            flw[s[i]]++, flw[t[i]]--;
        else 
            flw[t[i]]--, flw[s[i]]++;
    }

    int prv = 0;
    for (auto it = flw.begin(); it != flw.end(); it++) {
        it->sec += prv;
        prv = it->sec;
    }
    
    int ans = 0;
    for (auto it = flw.begin(); next(it, 1) != flw.end(); it++) {
        if (it->sec == 0) continue;
        if (it->sec > 0)
            ans += it->sec * (next(it, 1)->fir - it->fir);
        mrgd.push_back({it->fir, next(it, 1)->fir});
    }

    // for (pii x : flw)
    //     cerr << x.fir << ": " << x.sec << '\n';
    return ans;
}

struct Dsj {
    hmap<int, int> prnt, sz;
    void intl() {
        for (pii x : flw) prnt[x.fir] = x.fir, sz[x.fir] = 1;
    }
    int pr(int u) {
        return (prnt[u] == u) ? u : prnt[u] = pr(prnt[u]);
    }
    bool mrg(int u, int v) {
        u = pr(u), v = pr(v);
        if (u == v) return false;
        if (sz[u] < sz[v]) swap(u, v);
        prnt[v] = u, sz[u] += sz[v];
        return true;
    }
} dsj;
vec<vec<int>> edg;
int mst_cmp() {
    for (auto it = flw.begin(); next(it, 1) != flw.end(); it++)
        edg.push_back({next(it, 1)->fir - it->fir, it->fir, next(it, 1)->fir});
    sort(edg.begin(), edg.end());

    dsj.intl();
    for (int i = 0; i <= n; i++) dsj.mrg(s[i], t[i]);
    for (pii x : mrgd) dsj.mrg(x.fir, x.sec);

    int ans = 0;
    for (vec<int> x : edg) {
        int u = x[1], v = x[2];
        if (!dsj.mrg(u, v)) continue;
        // cerr << u << " " << v << '\n';
        ans += x[0];
    }
    return ans;
}

int plan_roller_coaster(vec<signed> _s, vec<signed> _t) {
    n = _s.size();
    for (int i = 1; i <= n; i++) s[i] = _s[i - 1], t[i] = _t[i - 1];
    s[0] = INF, t[0] = 1;

    int ans = flw_cmp();
    ans += mst_cmp();
    return ans;
}

Compilation message (stderr)

railroad.h:1:9: warning: #pragma once in main file
    1 | #pragma once
      |         ^~~~
railroad_c.h:1:9: warning: #pragma once in main file
    1 | #pragma once
      |         ^~~~

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