Submission #965018

#	Time	Username	Problem	Language	Result	Execution time	Memory
965018		Pannda	Swapping Cities (APIO20_swap)	C++17	17 / 100	2090 ms	524288 KiB

swap

#include "swap.h"

#include <bits/stdc++.h>
using namespace std;

struct DSU {
    vector<int> f;
    vector<int> siz;
    vector<int> deg;
    vector<int> ok;
    vector<vector<pair<int*, int>>> stk;

    DSU(int n) : f(n), siz(n, 1), deg(n, 0), ok(n, false) { iota(f.begin(), f.end(), 0); }

    int leader(int u) {
        while (u != f[u]) u = f[u];
        return u;
    }

    bool unionize(int u0, int v0) {
        stk.emplace_back();
        int u = leader(u0);
        int v = leader(v0);
        if (u == v) {
            stk.back().push_back({&ok[u], ok[u]}); ok[u] = true;
            return false;
        }
        if (siz[u] > siz[v]) swap(u, v);
        stk.back().push_back({&siz[v], siz[v]}); siz[v] += siz[u];
        stk.back().push_back({&deg[u0], deg[u0]}); deg[u0]++;
        stk.back().push_back({&deg[v0], deg[v0]}); deg[v0]++;
        stk.back().push_back({&ok[v], ok[v]}); if (deg[u0] >= 3 || deg[v0] >= 3) ok[v] = true; ok[v] = ok[v] | ok[u];
        stk.back().push_back({&f[u], f[u]}); f[u] = v;
        return true;
    }

    bool same(int u, int v) {
        return leader(u) == leader(v);
    }

    bool isOk(int u) {
        return ok[leader(u)];
    }

    void rollback() {
        for (auto [ptr, val] : stk.back()) {
            *ptr = val;
        }
        stk.pop_back();
    }
};
int n, m;
vector<array<int, 3>> edges;
const int B = 1600;
vector<DSU> dsus;
int b;

void init(int N, int M, vector<int> U, vector<int> V, vector<int> W) {
    n = N;
    m = M;
    edges.resize(m);
    for (int i = 0; i < m; i++) {
        edges[i] = {U[i], V[i], W[i]};
    }
    sort(edges.begin(), edges.end(), [&](array<int, 3> e0, array<int, 3> e1) { return e0[2] < e1[2]; });

    dsus.emplace_back(n);
    for (b = 0; B * b < m; b++) {
        dsus.push_back(dsus.back());
        for (int i = B * b; i < min(m, B * b + B); i++) {
            dsus.back().unionize(edges[i][0], edges[i][1]);
        }
    }
    b++;
}

int getMinimumFuelCapacity(int X, int Y) {
    if (!dsus.back().same(X, Y) || !dsus.back().isOk(X)) return -1;
    for (int b0 = 0; ; b0++) {
        if (dsus[b0 + 1].same(X, Y) && dsus[b0 + 1].isOk(X)) {
            int cnt = 0;
            int res;
            for (int i = B * b0; ; i++) {
                dsus[b0].unionize(edges[i][0], edges[i][1]);
                cnt++;
                if (dsus[b0].same(X, Y) && dsus[b0].isOk(X)) {
                    res = edges[i][2];
                    break;
                }
            }
            while (cnt--) dsus[b0].rollback();
            return res;
        }
    }
}

• Subtask 1: 0 / 6
• Subtask 2: 0 / 7
• Subtask 3: 17 / 17
• Subtask 4: 0 / 20
• Subtask 5: 0 / 23
• Subtask 6: 0 / 27