Submission #567493

#	Time	Username	Problem	Language	Result	Execution time	Memory
567493		Stickfish	Swapping Cities (APIO20_swap)	C++17	0 / 100	3 ms	4948 KiB

swap

#include "swap.h"
#include <vector>
#include <algorithm>
using namespace std;

const int MAXN = 1e5 + 123;
vector<pair<int, int>> edg[MAXN];
vector<pair<int, int>> edg_mst[MAXN];
int depth[MAXN];
int timer = 0;
int tin[MAXN];
int tout[MAXN];
pair<int, int> rt[MAXN];
pair<int, int> crt[MAXN];

void dfs(int v) {
    tin[v] = timer++;
    int rtv = rt[v].first;
    int crtrtv = crt[rtv].first;
    int crtcrtrtv = crt[crtrtv].first;
    if (depth[rtv] - depth[crtrtv] == depth[crtrtv] - depth[crtcrtrtv]) {
        crt[v] = {crtcrtrtv, max({rt[v].second, crt[rtv].second, crt[crtrtv].second})};
    }
    for (auto [u, w] : edg_mst[v]) {
        if (u == rt[v].first)
            continue;
        rt[u] = {v, w};
        depth[u] = depth[v] + 1;
    }
    tout[v] = timer;
}

struct dsu {
    void resize(int n) {
        par.resize(n);
        sz.assign(n, 1);
        for (int i = 0; i < n; ++i)
            par[i] = i;
    }

    int gst(int i) {
        if (par[i] == i)
            return i;
        return par[i] = gst(par[i]);
    }

    bool unite(int i, int j) {
        i = gst(i);
        j = gst(j);
        if (i == j)
            return false;
        if (sz[i] < sz[j])
            swap(i, j);
        par[j] = i;
        sz[i] += sz[j];
        return true;
    }
 private:
     vector<int> par;
     vector<int> sz;
};

pair<int, pair<int, int>> lca(int v, int u) {
    pair<int, int> ans;
    bool swp = 0;
    if (depth[u] > depth[v]) {
        swap(u, v);
        swp = 1;
    }
    while (depth[v] > depth[u]) {
        if (depth[crt[v].first] >= depth[u]) {
            ans.first = max(ans.first, crt[v].second);
            v = crt[v].first;
        } else {
            ans.first = max(ans.first, rt[v].second);
            v = rt[v].first;
        }
    }
    while (v != u) {
        if (crt[v].first == crt[u].first) {
            ans.first = max(ans.first, rt[v].second);
            v = rt[v].first;
            ans.second = max(ans.second, rt[u].second);
            u = rt[u].first;
        } else {
            ans.first = max(ans.first, crt[v].second);
            v = crt[v].first;
            ans.second = max(ans.second, crt[u].second);
            u = crt[u].first;
        }
    }
    if (swp)
        swap(ans.first, ans.second);
    return {v, ans};
}

void init(int n, int m, vector<int> U, vector<int> V, vector<int> W) {
    vector<pair<int, pair<int, int>>> edg_weight(m);
    for (int i = 0; i < m; ++i) {
        edg_weight[i] = {W[i], {U[i], V[i]}};
    }
    sort(edg_weight.begin(), edg_weight.end());
    dsu su;
    su.resize(n);
    for (auto [w, e] : edg_weight) {
        auto [u, v] = e;
        if (su.unite(u, v)) {
            edg_mst[u].push_back({v, w});
            edg_mst[v].push_back({u, w});
        }
    }
    dfs(0);
}

int getMinimumFuelCapacity(int X, int Y) {
    auto la = lca(X, Y);
    return max(la.second.first, la.second.second);
}

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