Submission #688514

#	Time	Username	Problem	Language	Result	Execution time	Memory
688514		stevancv	Railway (BOI17_railway)	C++14	100 / 100	142 ms	37548 KiB

railway

#include <bits/stdc++.h>
#define ll long long
#define ld long double
#define sp ' '
#define en '\n'
#define smin(a, b) a = min(a, b)
#define smax(a, b) a = max(a, b)
using namespace std;
const int N = 1e5 + 2;
const int inf = 1e9;
vector<array<int, 2>> g[N], ch[N];
vector<int> a[N], st[N], ans;
int par[N][17], in[N], out[N], tsz, k;
struct Bit {
    int bit[N];
    void Add(int x, int v) {
        for (; x < N; x += x & (-x)) bit[x] += v;
    }
    int Get(int x) {
        int ans = 0;
        for (; x > 0; x -= x & (-x)) ans += bit[x];
        return ans;
    }
}f;
void Dfs(int s, int e) {
    in[s] = ++tsz;
    par[s][0] = e;
    for (int i = 1; i < 17; i++) par[s][i] = par[par[s][i - 1]][i - 1];
    for (auto u : g[s]) {
        if (u[0] == e) continue;
        Dfs(u[0], s);
    }
    out[s] = tsz;
}
bool Ancestor(int u, int v) {
    return in[u] <= in[v] && out[v] <= out[u];
}
int Lca(int u, int v) {
    if (Ancestor(u, v)) return u;
    if (Ancestor(v, u)) return v;
    for (int i = 16; i >= 0; i--) {
        if (par[u][i] && !Ancestor(par[u][i], v)) u = par[u][i];
    }
    return par[u][0];
}
void Solve(int s, int e) {
    for (int u : st[s]) f.Add(in[a[u][0]], 1);
    for (auto u : ch[s]) {
        f.Add(in[a[u[0]][u[1]]], -1);
        if (u[1] < a[u[0]].size() - 1) f.Add(in[a[u[0]][u[1] + 1]], 1);
    }
    for (auto u : g[s]) {
        if (u[0] == e) continue;
        if (f.Get(out[u[0]]) - f.Get(in[u[0]] - 1) >= k) ans.push_back(u[1]);
        Solve(u[0], s);
    }
    for (int u : st[s]) f.Add(in[a[u][0]], -1);
}
int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int n, s;
    cin >> n >> s >> k;
    for (int i = 1; i < n; i++) {
        int u, v;
        cin >> u >> v;
        g[u].push_back({v, i});
        g[v].push_back({u, i});
    }
    Dfs(1, 0);
    for (int i = 1; i <= s; i++) {
        int sz; cin >> sz;
        a[i].resize(sz);
        for (int j = 0; j < sz; j++) cin >> a[i][j];
        sort(a[i].begin(), a[i].end(), [&] (int ii, int jj) {
            return in[ii] < in[jj];
        });
        int lca = a[i][0];
        for (int j = 1; j < sz; j++) lca = Lca(lca, a[i][j]);
        st[lca].push_back(i);
        for (int j = 0; j < sz; j++) ch[a[i][j]].push_back({i, j});
    }
    Solve(1, 0);
    sort(ans.begin(), ans.end());
    cout << ans.size() << en;
    for (int u : ans) cout << u << sp;
    cout << en;
    return 0;
}

Compilation message (stderr)

railway.cpp: In function 'void Solve(int, int)':
railway.cpp:50:18: warning: comparison of integer expressions of different signedness: 'std::array<int, 2>::value_type' {aka 'int'} and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   50 |         if (u[1] < a[u[0]].size() - 1) f.Add(in[a[u[0]][u[1] + 1]], 1);

• Subtask 1: 8 / 8
• Subtask 2: 15 / 15
• Subtask 3: 7 / 7
• Subtask 4: 29 / 29
• Subtask 5: 16 / 16
• Subtask 6: 25 / 25