Submission #1022671

#	Time	Username	Problem	Language	Result	Execution time	Memory
1022671		PurpleCrayon	Chameleon's Love (JOI20_chameleon)	C++17	100 / 100	38 ms	1120 KiB

chameleon

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

#define sz(v) int(v.size())
#define ar array
typedef long long ll;
const int N = 5e2+10, MOD = 1e9+7;

namespace {

}  // namespace

vector<int> adj[2 * N];
vector<int> vis; 

void dfs_col(int c, int b) {
    vis[c] = b;
    for (int nxt : adj[c]) if (vis[nxt] == -1)
        dfs_col(nxt, b ^ 1);
}

vector<int> build_cols(vector<pair<int, int>> edges, int l, int r) {
    vis.assign(r + 1, -1);
    for (int i = l; i <= r; i++)
        adj[i].clear();

    for (auto [a, b] : edges)
        adj[a].push_back(b), adj[b].push_back(a);

    for (int i = l; i <= r; i++) if (vis[i] == -1)
        dfs_col(i, 0);

    return vis;
}

vector<pair<int, int>> rec(int l, int r) {
    if (l >= r) return {};
    auto edges = rec(l + 1, r);
    vector<int> cnt(r + 1);
    for (auto [a, b] : edges)
        cnt[a]++, cnt[b]++;

    auto cols = build_cols(edges, l + 1, r);
    vector<int> one, two;
    for (int i = l + 1; i <= r; i++) {
        if (cnt[i] == 3) continue;
        if (cols[i])
            one.push_back(i);
        else
            two.push_back(i);
    }


    for (int rep = 0; rep < 2; rep++) if (cnt[l] < 3) {
        auto check = [&](int L, int R) {
            vector<int> v{l};
            for (int j = L; j <= R; j++)
                v.push_back(one[j]);

            if (Query(v) != sz(v))
                return true;
            else
                return false;
        };
        int L = 0;
        while (L < sz(one) && cnt[l] < 3) {
            if (!check(L, sz(one)-1))
                break;

            int lo = -1, hi = sz(one)-1, mid = (lo + hi) / 2;
            while (lo < mid && mid < hi) {
                if (check(L, mid)) hi = mid;
                else lo = mid;
                mid = (lo + hi) / 2;
            }

            edges.emplace_back(l, one[hi]);
            cnt[l]++, cnt[one[hi]]++;
            L = hi + 1;
        }

        swap(one, two);
    }

    return edges;
}

void Solve(int n) {
    auto edges = rec(1, 2*n);
    vector<vector<int>> adj(2 * n + 1);
    vector<int> out(2 * n + 1);
    for (auto [a, b] : edges) {
        adj[a].push_back(b);
        adj[b].push_back(a);
    }

    for (int i = 1; i <= 2 * n; i++) {
        if (sz(adj[i]) == 1) {
            continue;
        }

        assert(sz(adj[i]) == 3);
        random_shuffle(adj[i].begin(), adj[i].end());
        out[i] = adj[i][2];
        for (int j = 0; j <= 1; j++) if (out[adj[i][j]] != i) {
            vector<int> v{i};
            for (int k = 0; k < 3; k++) if (k != j)
                v.push_back(adj[i][k]);

            if (Query(v) == 1) {
                out[i] = adj[i][j];
                break;
            }
        }
    }

    for (int a = 1; a <= 2 * n; a++) {
        for (int b : adj[a]) {
            if (out[a] == b) continue;
            if (out[b] == a) continue;
            if (a > b) continue;
            Answer(a, b);
        }
    }
}

• Subtask 1: 4 / 4
• Subtask 2: 20 / 20
• Subtask 3: 20 / 20
• Subtask 4: 20 / 20
• Subtask 5: 36 / 36