Submission #965068

#	Time	Username	Problem	Language	Result	Execution time	Memory
965068		Pannda	Swapping Cities (APIO20_swap)	C++17	43 / 100	2083 ms	434564 KiB

swap

#include "swap.h"

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

struct DSU {
    vector<int> f;
    vector<int> siz;
    vector<int> deg;
    vector<bool> ok;

    DSU() {}
    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] = f[f[u]];
        return u;
    }

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

struct LiteDSU {
    vector<int> f;
    vector<int> siz;
    vector<bool> ok;

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

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

    bool unionize(int u, int v) {
        u = leader(u);
        v = leader(v);
        if (u == v) return false;
        if (siz[u] > siz[v]) swap(u, v);
        siz[v] += siz[u];
        ok[v] = ok[v] | ok[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)];
    }
};

int n, m;
vector<array<int, 3>> edges;
const int B = 380;
DSU dsu;
struct Block {
    int c;
    vector<int> dom;
    vector<int> f;
    vector<int> deg;
    vector<bool> ok;

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

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

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

    Block(int n, int b, DSU &dsu0, DSU &dsu1, vector<array<int, 3>> &edges) {
        f = dsu0.f;
        deg = dsu0.deg;
        ok = dsu0.ok;
        vector<int> mp(n, -1);
        for (int i = B * b; i < min(m, B * b + B); i++) {
            int u = dsu0.leader(edges[i][0]);
            int v = dsu0.leader(edges[i][1]);
            if (mp[u] == -1) mp[u] = 0, dom.push_back(u);
            if (mp[v] == -1) mp[v] = 0, dom.push_back(v);
        }
        c = dom.size();
    }
};
vector<Block> blocks;
vector<int> mp;

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]; });

    dsu = DSU(n);
    for (int b = 0; B * b < m; b++) {
        DSU next_dsu = dsu;
        for (int i = B * b; i < min(m, B * b + B); i++) {
            next_dsu.unionize(edges[i][0], edges[i][1]);
        }
        blocks.push_back(Block(n, b, dsu, next_dsu, edges));
        dsu = next_dsu;
    }
    mp.resize(n, -1);
}

int getMinimumFuelCapacity(int X, int Y) {
    if (!dsu.same(X, Y) || !dsu.isOk(X)) return -1;
    int b = [&]() -> int {
        int l = 0, r = (int)blocks.size() - 1;
        while (l < r) {
            int m = (l + r + 1) >> 1;
            if (!blocks[m].same(X, Y) || !blocks[m].isOk(X)) {
                l = m;
            } else {
                r = m - 1;
            }
        }
        return l;
    }();
    int label = 0;
    for (int u : blocks[b].dom) mp[u] = label++;
    int x = mp[blocks[b].leader(X)];
    int y = mp[blocks[b].leader(Y)];
    LiteDSU dsu(blocks[b].c);
    int res = -2;
    vector<int> defer;
    for (int u : blocks[b].dom) if (blocks[b].isOk(u)) dsu.ok[mp[u]] = true;
    for (int i = B * b; i < min(m, B * b + B); i++) {
        int u = mp[blocks[b].leader(edges[i][0])];
        int v = mp[blocks[b].leader(edges[i][1])];
        if (dsu.same(u, v)) {
            dsu.ok[dsu.leader(u)] = true;
        } else {
            defer.push_back(edges[i][0]);
            defer.push_back(edges[i][1]);
            if (++blocks[b].deg[edges[i][0]] >= 3) dsu.ok[dsu.leader(u)] = true;
            if (++blocks[b].deg[edges[i][1]] >= 3) dsu.ok[dsu.leader(v)] = true;
            dsu.unionize(u, v);
        }
        if (dsu.same(x, y) && dsu.isOk(x)) {
            res = edges[i][2];
            break;
        }
    }
    for (int u : defer) blocks[b].deg[u]--;
    for (int u : blocks[b].dom) mp[u] = -1;
    return res;
}

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