Submission #786293

#	Time	Username	Problem	Language	Result	Execution time	Memory
786293		chanhchuong123	Railway (BOI17_railway)	C++14	100 / 100	175 ms	46100 KiB

railway

#include <bits/stdc++.h>
using namespace std;
#define task ""
#define fi first
#define se second
#define all(x) x.begin(), x.end()
#define FOR(i, a, b) for (int i = (a), _b = (b); i <= _b; ++i)
#define FORD(i, a, b) for (int i = (b), _a = (a); i >= _a; --i)

template <typename T1, typename T2> bool minimize(T1 &a, T2 b) {
	if (a > b) {a = b; return true;} return false;
}
template <typename T1, typename T2> bool maximize(T1 &a, T2 b) {
	if (a < b) {a = b; return true;} return false;
}

const int dx[] = {-1, 0, 0, +1};
const int dy[] = {0, -1, +1, 0};

const int MAX = 100100;
int n, k, m;
int ID[MAX];
vector<int> res;
set<int> add[MAX];
vector<int> del[MAX];
int h[MAX], anc[17][MAX];
vector<pair<int, int>> adj[MAX];

void dfs(int u, int p) {
    for (pair<int, int> &x: adj[u]) if (x.fi != p) {
        int v = x.fi;
        ID[v] = x.se;
        anc[0][v] = u;
        h[v] = h[u] + 1;
        for (int j = 1; j <= 16; ++j) {
            anc[j][v] = anc[j - 1][anc[j - 1][v]];
        }
        dfs(v, u);
    }
}

int lca(int u, int v) {
    if (h[u] < h[v]) swap(u, v);
    int k = h[u] - h[v];
    for (int j = 0; (1 << j) <= k; ++j) {
        if (k >> j & 1) u = anc[j][u];
    }
    if (u == v) return u;
    for (int j = 16; j >= 0; --j) {
        if (anc[j][u] != anc[j][v]) {
            u = anc[j][u];
            v = anc[j][v];
        }
    }
    return anc[0][u];
}

void reDfs(int u, int p) {
    for (pair<int, int> &x: adj[u]) if (x.fi != p) {
        int v = x.fi; reDfs(v, u); if (add[u].size() < add[v].size()) add[u].swap(add[v]);
        for (int x: add[v]) add[u].insert(x);
    }
    for (int &x: del[u]) add[u].erase(x);
    if (add[u].size() >= k && u != 1) {
        res.push_back(ID[u]);
    }
}

int main() {
	ios_base::sync_with_stdio(false); cin.tie(nullptr);

	if (fopen(task".inp", "r")) {
		freopen(task".inp", "r", stdin);
		freopen(task".out", "w", stdout);
	}

	cin >> n >> m >> k;
	for (int i = 1; i < n; ++i) {
        int u, v; cin >> u >> v;
        adj[u].push_back({v, i});
        adj[v].push_back({u, i});
	}
	dfs(1, -1);
	for (int i = 1; i <= m; ++i) {
        int s, c, u; cin >> s >> c;
        --s; add[c].insert(i);
        while (s--) {
            cin >> u;
          	c = lca(c, u);
            add[u].insert(i);
        }
        del[c].push_back(i);
	}
	reDfs(1, -1);
	sort(all(res));
	cout << res.size() << '\n';
	for (int &x: res) cout << x << ' ';

	return 0;
}

Compilation message (stderr)

railway.cpp: In function 'void reDfs(int, int)':
railway.cpp:64:23: warning: comparison of integer expressions of different signedness: 'std::set<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   64 |     if (add[u].size() >= k && u != 1) {
      |         ~~~~~~~~~~~~~~^~~~
railway.cpp: In function 'int main()':
railway.cpp:73:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   73 |   freopen(task".inp", "r", stdin);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
railway.cpp:74:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   74 |   freopen(task".out", "w", stdout);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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