Submission #443140

#	Time	Username	Problem	Language	Result	Execution time	Memory
443140		blue	Mergers (JOI19_mergers)	C++17	0 / 100	84 ms	37008 KiB

mergers

#include <iostream>
#include <set>
#include <vector>
using namespace std;

const int maxN = 500'000;

vector<int> edge[1+maxN];
vector<int> parent(1+maxN, 0);
vector<int> subtree(1+maxN, 1);
vector<int> max_child(1+maxN, -1);

void dfs1(int u)
{
    for(int v: edge[u])
    {
        if(parent[u] == v) continue;
        parent[v] = u;
        dfs1(v);
        subtree[u] += subtree[v];
        if(max_child[u] == -1 || subtree[v] > subtree[ max_child[u] ])
            max_child[u] = v;
    }
}




struct state
{
    int i;
    int c;
};

bool operator < (state A, state B)
{
    return A.i < B.i;
}

int S[1+maxN];
vector<int> state_count(1+maxN, 0);

set<state>* T[1+maxN];



void add_state(int u, state x)
{
    // cerr << "add_state " << u << ' ' << x.i << ' ' << x.c << '\n';
    set<state>::iterator it = T[u]->find(x);
    if(it == T[u]->end())
    {
        // cerr << "case A\n";
        if(x.c != state_count[x.i])
            T[u]->insert(x);
    }
    else
    {
        // cerr << "case B\n";
        int ct = it->c + x.c;
        T[u]->erase(it);
        if(ct != state_count[x.i])
        {
            T[u]->insert(state{x.i, ct});
        }
    }
}

int bad_edge_count = 0;

bool dfs2(int u) //returns if we have found any bad edges yet.
{
    // cerr << "dfs2 " << u << ' ' << max_child[u] << '\n';
    bool flag = 0;
    if(max_child[u] == -1)
    {
        // cerr << "case 1\n";
        T[u] = new set<state>;
        add_state(u, state{S[u], 1});
    }
    else
    {
        for(int v: edge[u])
        {
            if(v == parent[u]) continue;
            // cerr << u << " -> " << v << '\n';
            flag |= dfs2(v);
        }

        // cerr << "case 2\n";
        T[u] = T[ max_child[u] ];
        // cerr << "x\n";
        add_state(u, state{S[u], 1});
        // cerr << "check X\n";
        for(int v: edge[u])
        {
            // cerr << "v = " << v << '\n';
            if(v == parent[u] || v == max_child[u]) continue;

            for(state s: *(T[v]))
                add_state(u, s);

            T[v]->clear();
        }
    }

    if(T[u]->size() == 0 && u != 1)
    {
        if(!flag)
        {
            // cerr << "adding bad edge at " << u << '\n';
            bad_edge_count++;
        }
        return 1;
    }
    else
    {
        return flag;
    }

}






int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    
    int N, K;
    cin >> N >> K;

    for(int i = 1; i <= N-1; i++)
    {
        int A, B;
        cin >> A >> B;
        edge[A].push_back(B);
        edge[B].push_back(A);
    }

    for(int i = 1; i <= N; i++)
    {
        cin >> S[i];
        state_count[ S[i] ]++;
    }

    // cerr << "check 0\n";

    parent[1] = 1;
    dfs1(1);

    // cerr << "check 1\n";

    dfs2(1);

    // cerr << "check 2\n";

    int res = (bad_edge_count / 2) + (bad_edge_count % 2);

    cout << res << '\n';
}

• Subtask 1: 0 / 10
• Subtask 2: 0 / 24
• Subtask 3: 0 / 14
• Subtask 4: 0 / 22
• Subtask 5: 0 / 30