Submission #341113

#	Time	Username	Problem	Language	Result	Execution time	Memory
341113		ijxjdjd	Mergers (JOI19_mergers)	C++14	100 / 100	1568 ms	147672 KiB

mergers

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

using ll = long long;
const int MAXN = (int)(5e5) + 5;
vector<int> adj[MAXN];
int up[MAXN][21];
int timer = 0;
int tin[MAXN];
int tout[MAXN];
int S[MAXN];
int last[MAXN];
int lcm[MAXN];
int cnt[MAXN];
void root(int n, int p) {
    tin[n] = timer++;
    up[n][0] = p;
    for (int k = 1; k <= 20; k++) {
        up[n][k] = up[up[n][k-1]][k-1];
    }
    for (int e : adj[n]) {
        if (e != p) {
            root(e, n);
        }
    }
    tout[n] = timer++;
}
vector<int> dfs(int n, int p) {
    int paths = 0;
    vector<int> arr(3, 0);
    arr[2] = (int)(1e6);
    arr[1] = (int)(1e6);
    for (int e : adj[n]) {
        if (e != p) {
            vector<int> next = dfs(e, n);
            vector<int> old = arr;
            fill(arr.begin(), arr.end(), (int)(1e6));
            for (int i = 0; i < 3; i++) {
                for (int j = 0; j < 3; j++) {
                    if (i + j == 4) {
                        arr[2] = min(old[i] + next[j] + 1, arr[2]);
                        arr[0] = min(old[i] + next[j] + 2, arr[0]);
                    }
                    else if (i + j == 3) {
                        arr[1] = min(old[i] + next[j] + 1, arr[1]);
                    }
                    else if (i + j == 2) {
                        if (i == 2 || j ==2) {
                            arr[2] = min(arr[2], old[i] + next[j]);
                        }
                        else {
                            arr[2] = min(arr[2], old[i] + next[j]);
                            arr[0] = min(arr[0], old[i] + next[j] + 1);
                        }
                    }
                    else if (i + j == 1) {
                        arr[1] = min(arr[1], old[i] + next[j]);
                    }
                    else {
                        arr[0] = min(arr[0], old[i] + next[j]);
                    }
                }
            }
            cnt[n] += cnt[e];
        }
    }
    if (cnt[n] == 0) {
        if (n != p) {
            arr[1] = min(arr[0], arr[1]);
            arr[0] = (int)(1e6);
        }
    }
    return arr;
}
bool is_ancestor(int a, int b) {
    return (tin[a] <= tin[b] && tout[a] >= tout[b]);
}
int lca(int a, int b) {
    if (is_ancestor(a, b)) {
        return a;
    }
    if (is_ancestor(b, a)) {
        return b;
    }
    int u = a;
    for (int k = 20; k >= 0; k--) {
        if (!is_ancestor(up[u][k], b)) {
            u = up[u][k];
        }
    }
    return up[u][0];
}
int main() {
    string asdf = "input.in";
    int N, s;
    cin >> N >> s;
    for (int i = 0; i < N-1; i++) {
        int a, b;
        cin >> a >> b;
        a--, b--;
        adj[a].push_back(b);
        adj[b].push_back(a);
    }
    vector<int> df;
    for (int i = 0; i < N; i++) {
        df.push_back(i);
        last[i] = -1;
        cin >> S[i];
        S[i]--;
    }
    root(0, 0);
    sort(df.begin(), df.end(), [](const int& lhs, const int& rhs) {
            return tin[lhs] < tin[rhs];
         }
     );
    for (int i : df) {
        if (last[S[i]] == -1) {
            last[S[i]] = i;
            lcm[S[i]] = i;
        }
        else {
            if (is_ancestor(lcm[S[i]], i)) {
                cnt[i]++;
                cnt[lcm[S[i]]]--;
            }
            else {
                int lc = lca(lcm[S[i]], i);
                cnt[lcm[S[i]]]++;
                cnt[lc]-=2;
                cnt[i]++;
                lcm[S[i]] = lc;
            }
        }
    }
    vector<int> ans = dfs(0, 0);
    cout << min(ans[0], ans[1]+1);
    return 0;
}

Compilation message (stderr)

mergers.cpp: In function 'std::vector<int> dfs(int, int)':
mergers.cpp:29:9: warning: unused variable 'paths' [-Wunused-variable]
   29 |     int paths = 0;
      |         ^~~~~

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