Submission #1245553

#	Time	Username	Problem	Language	Result	Execution time	Memory
1245553		ducdev	Pastiri (COI20_pastiri)	C++20	8 / 100	324 ms	102068 KiB

pastiri

// Author: 4uckd3v - Nguyen Cao Duc
#include <bits/stdc++.h>
using namespace std;

typedef long long ll;

const int MAX_N = 5e5;
const int MOD = 1e9 + 7;
const int INF = 1e9;

template <class X, class Y>
bool minimize(X &x, const Y &y) {
    if (x <= y) return false;
    x = y;
    return true;
};

int n, k, timer, lg;
int sheepIdx[MAX_N + 5], depth[MAX_N + 5], tin[MAX_N + 5], tout[MAX_N + 5];
int up[MAX_N + 5][20];
vector<int> adj[MAX_N + 5];

void preDfs(int u, int par) {
    tin[u] = ++timer;
    up[u][0] = par;
    depth[u] = depth[par] + 1;

    for (int i = 1; i <= lg; i++)
        up[u][i] = up[up[u][i - 1]][i - 1];

    for (int v : adj[u]) {
        if (v == par) continue;
        preDfs(v, u);
    };

    tout[u] = ++timer;
};

bool isAncestor(int u, int v) {
    return tin[u] <= tin[v] && tout[u] >= tout[v];
};

int __lca(int u, int v) {
    if (isAncestor(u, v)) return u;
    if (isAncestor(v, u)) return v;

    for (int i = lg; i >= 0; i--)
        if (!isAncestor(up[u][i], v))
            u = up[u][i];

    return up[u][0];
};

int dist(int u, int v) {
    return depth[u] + depth[v] - 2 * depth[__lca(u, v)];
};

namespace SUBTASK_1 {
    const int N = 5e5;

    int dp[N + 5];

    bool checkSubtask() {
        for (int u = 1; u <= n; u++)
            if (adj[u].size() > 2) return false;
        return true;
    };

    void trace(int i) {
        vector<int> t;
        while (i > 0) {
            if (dp[i] == dp[i - 1] + 1) {
                t.push_back(sheepIdx[i]);
                i--;
            } else {
                int prevIdx = sheepIdx[i - 1];
                int curIdx = sheepIdx[i];
                t.push_back((curIdx + prevIdx + 1) >> 1);
                i -= 2;
            };
        };

        for (int idx : t) cout << idx << ' ';
        cout << '\n';
    };

    void Solve() {
        for (int i = 1; i <= n; i++) dp[i] = INF;

        dp[1] = 1;

        for (int i = 2; i <= k; i++) {
            int prevIdx = sheepIdx[i - 1];
            int curIdx = sheepIdx[i];

            if ((curIdx - prevIdx + 1) & 1) {
                minimize(dp[i], dp[i - 2] + 1);
            };

            minimize(dp[i], dp[i - 1] + 1);
        };

        cout << dp[k] << '\n';
        trace(k);
    };
};  // namespace SUBTASK_1

namespace SUBTASK_2 {
    const int N = MAX_N;
    const int K = 15;

    int dp[1 << K], node[1 << K];

    bool checkSubtask() {
        return k <= K && n <= N;
    };

    void trace(int mask) {
        while (mask > 0) {
            for (int subMask = mask; subMask > 0; subMask &= (subMask - 1) & mask) {
                if (node[subMask] == 0) continue;
                if (dp[mask] == dp[mask ^ subMask] + dp[subMask]) {
                    cout << node[subMask] << ' ';
                    mask ^= subMask;
                    break;
                };
            };
        };
    };

    void Solve() {
        for (int mask = 0; mask < (1 << k); mask++) dp[mask] = INF;

        dp[0] = 0;
        for (int u = 1; u <= n; u++) {
            int minDist = INF;
            int mask = 0;
            for (int j = 1; j <= k; j++) {
                int v = sheepIdx[j];
                if (minimize(minDist, dist(u, v))) {
                    mask = 1 << (j - 1);
                } else if (minDist == dist(u, v)) {
                    mask |= 1 << (j - 1);
                };
            };
            if (mask > 0) {
                node[mask] = u;
            };
        };

        for (int mask = 0; mask < (1 << k); mask++) {
            for (int subMask = mask; subMask > 0; subMask &= (subMask - 1) & mask) {
                if (node[subMask] == 0) continue;
                minimize(dp[mask], dp[mask ^ subMask] + 1);
            };
        };

        cout << dp[(1 << k) - 1] << '\n';
        trace((1 << k) - 1);
    };
};  // namespace SUBTASK_2

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    if (fopen("PASTIRI.INP", "r")) {
        freopen("PASTIRI.INP", "r", stdin);
        freopen("PASTIRI.OUT", "w", stdout);
    };

    cin >> n >> k;
    for (int i = 1; i < n; i++) {
        int u, v;
        cin >> u >> v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    };

    lg = ceil(log2(n));
    preDfs(1, 1);

    for (int i = 1; i <= k; i++) {
        cin >> sheepIdx[i];
    };

    sort(sheepIdx + 1, sheepIdx + k + 1);

    if (SUBTASK_1::checkSubtask())
      return SUBTASK_1::Solve(), 0;
    if (SUBTASK_2::checkSubtask())
      return SUBTASK_2::Solve(), 0;
};

Compilation message (stderr)

pastiri.cpp: In function 'int main()':
pastiri.cpp:167:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  167 |         freopen("PASTIRI.INP", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
pastiri.cpp:168:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  168 |         freopen("PASTIRI.OUT", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 8 / 8
• Subtask 2: 0 / 18
• Subtask 3: 0 / 23
• Subtask 4: 0 / 51