Submission #723536

#	Time	Username	Problem	Language	Result	Execution time	Memory
723536		t6twotwo	Village (BOI20_village)	C++17	56 / 100	111 ms	27808 KiB

Village

#include <bits/stdc++.h>
using namespace std;
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int n;
    cin >> n;
    vector<vector<int>> adj(n);
    for (int i = 1; i < n; i++) {
        int x; cin >> x; x--;
        int y; cin >> y; y--;
        adj[x].push_back(y);
        adj[y].push_back(x);
    }
    vector<int> amin(n);
    iota(amin.begin(), amin.end(), 0);
    int ansmin = 0;
    auto dfs = [&](auto dfs, int x, int p) -> bool {
        vector<int> b;
        for (int y : adj[x]) {
            if (y != p) {
                if (dfs(dfs, y, x)) {
                    b.push_back(y);
                }
            }
        }
        if (b.empty()) {
            return 1;
        }
        ansmin += b.size() * 2;
        if (b.size() % 2 == 1) {
            swap(amin[x], amin[b[0]]);
            for (int i = 1; i < b.size(); i += 2) {
                swap(amin[b[i]], amin[b[i + 1]]);
            }
        } else {
            swap(amin[x], amin[b[0]]);
            swap(amin[x], amin[b[1]]);
            for (int i = 2; i < b.size(); i += 2) {
                swap(amin[b[i]], amin[b[i + 1]]);
            }
        }
        return 0;
    };
    if (dfs(dfs, 0, -1)) {
        swap(amin[0], amin[adj[0][0]]);
        ansmin += 2;
    }
    set<int> s;
    for (int i = 0; i < n; i++) {
        s.insert(i);
    }
    auto bfs = [&](int src) {
        vector<int> dis(n, -1);
        queue<int> q;
        dis[src] = 0;
        q.push(src);
        while (!q.empty()) {
            int x = q.front();
            q.pop();
            for (int y : adj[x]) {
                if (dis[y] == -1 && s.count(y)) {
                    dis[y] = dis[x] + 1;
                    q.push(y);
                }
            }
        }
        return dis;
    };
    vector<int> amax(n);
    iota(amax.begin(), amax.end(), 0);
    int64_t ansmax = 0;
    if (n <= 1000) {
        while (s.size() > 1) {
            int t =  *s.begin();
            auto dis = bfs(t);
            int u = max_element(dis.begin(), dis.end()) - dis.begin();
            dis = bfs(u);
            int v = max_element(dis.begin(), dis.end()) - dis.begin();
            swap(amax[u], amax[v]);
            ansmax += 2 * dis[v];
            s.erase(u);
            s.erase(v);
        }
        if (s.size() == 1) {
            int x = *s.begin();
            swap(amax[x], amax[adj[x][0]]);
        }
    }
    cout << ansmin << " " << ansmax << "\n";
    for (int i = 0; i < n; i++) {
        cout << amin[i] + 1 << " \n"[i == n - 1];
    }
    for (int i = 0; i < n; i++) {
        cout << amax[i] + 1 << " \n"[i == n - 1];
    }
    return 6/22;
}

Compilation message (stderr)

Village.cpp: In lambda function:
Village.cpp:33:31: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   33 |             for (int i = 1; i < b.size(); i += 2) {
      |                             ~~^~~~~~~~~~
Village.cpp:39:31: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   39 |             for (int i = 2; i < b.size(); i += 2) {
      |                             ~~^~~~~~~~~~
Village.cpp: In instantiation of 'main()::<lambda(auto:23, int, int)> [with auto:23 = main()::<lambda(auto:23, int, int)>]':
Village.cpp:45:23:   required from here
Village.cpp:33:31: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   33 |             for (int i = 1; i < b.size(); i += 2) {
      |                             ~~^~~~~~~~~~
Village.cpp:39:31: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   39 |             for (int i = 2; i < b.size(); i += 2) {
      |                             ~~^~~~~~~~~~

• Subtask 1: 12 / 12
• Subtask 2: 19 / 38
• Subtask 3: 25 / 50