Submission #990968

#	Time	Username	Problem	Language	Result	Execution time	Memory
990968		tincamatei	Cat Exercise (JOI23_ho_t4)	C++14	100 / 100	171 ms	45728 KiB

Main

#include <bits/stdc++.h>

struct DSU {
    std::vector<long long> height;
    std::vector<int> boss;

    explicit DSU(int N) {
        boss.resize(1 + N);
        height.resize(1 + N);
        for (int i = 1; i <= N; i++)
            boss[i] = i;
    }

    int find(int x) {
        if (x == boss[x])
            return x;

        boss[x] = find(boss[x]);
        return boss[x];
    }

    void merge(int a, int b) {
        int sa = find(a);
        int sb = find(b);

        if (sa > sb)
            boss[sb] = sa;
        else
            boss[sa] = sb;
    }
};

struct DistanceCalculator {
    int lg = 0;
    std::vector<std::vector<int>>& graph;
    std::vector<std::vector<int>> parent;

    std::vector<int> dep;

    DistanceCalculator(std::vector<std::vector<int>>& _graph): graph(_graph) {
        int N = (int)graph.size() - 1;
        while ((1 << (lg + 1)) <= N)
            lg++;

        parent.resize(1 + N, std::vector<int>(1 + lg));
        dep.resize(1 + N);

        predfs();
    }

    void predfs(int node = 1, int father = 0) {
        parent[node][0] = father;
        for (int l = 1; l <= lg; l++)
            parent[node][l] = parent[parent[node][l - 1]][l - 1];

        for (auto it: graph[node]) {
            if (it != father) {
                dep[it] = dep[node] + 1;
                predfs(it, node);
            }
        }
    }

    int goup(int node, int x) {
        for (int l = lg; l >= 0; --l)
            if ((1 << l) & x)
                node = parent[node][l];
        return node;
    }

    int lca(int a, int b) {
        if (dep[a] > dep[b])
            a = goup(a, dep[a] - dep[b]);
        else
            b = goup(b, dep[b] - dep[a]);

        if (a == b) return a;

        for (int l = lg; l >= 0; --l)
            if (parent[a][l] != parent[b][l]) {
                a = parent[a][l];
                b = parent[b][l];
            }
        return parent[a][0];
    }

    int dist(int a, int b) {
        int l = lca(a, b);
        return dep[a] + dep[b] - 2 * dep[l];
    }
};

int main() {
    std::cin.tie(NULL);
    std::iostream::sync_with_stdio(false);

    int N;
    std::cin >> N;

    std::vector<int> perm(1 + N);
    
    for (int i = 1; i <= N; i++)
        std::cin >> perm[i];

    std::vector<std::vector<int>> graph(1 + N);

    for (int i = 0; i < N - 1; i++) {
        int a, b;
        std::cin >> a >> b;
        a = perm[a];
        b = perm[b];

        graph[a].push_back(b);
        graph[b].push_back(a);
    }

    DSU dsu(N);
    DistanceCalculator dc(graph);

    //std::cerr << dc.dist(2, 3) << "\n";

    for (int node = 1; node <= N; node++) {
        long long height = 0;
        for (auto it: graph[node]) {
            if (node > it) {
                height = std::max(height, dsu.height[dsu.find(it)] + dc.dist(node, dsu.find(it)));
                dsu.merge(node, it);
            }
        }

        dsu.height[dsu.find(node)] = height;
        //std::cerr << node << " has height " << height << "\n";
    }

    std::cout << dsu.height[dsu.find(N)];

    return 0;
}

• Subtask 1: 7 / 7
• Subtask 2: 7 / 7
• Subtask 3: 7 / 7
• Subtask 4: 10 / 10
• Subtask 5: 20 / 20
• Subtask 6: 23 / 23
• Subtask 7: 26 / 26