Submission #1105425

#	Time	Username	Problem	Language	Result	Execution time	Memory
1105425		tradz	Railway (BOI17_railway)	C++14	100 / 100	75 ms	85696 KiB

railway

#include <bits/stdc++.h>
#define TIME  (1.0 * clock() / CLOCKS_PER_SEC)
#define For(i,a,b) for(int i = a; i <= b; i++)
#define Ford(i,a,b) for(int i = a; i >= b; i--)
#define ll long long
#define ii pair<int,int>
#define fi first
#define se second
#define all(v) v.begin(),v.end()
#define RRH(v) v.resize(unique(all(v)) - v.begin())

using namespace std;
const int  N = 1e6+7;
const int M = 1e9+7;
const ll oo = 3e18;

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());

long long GetRandom(long long l, long long r) {
    return uniform_int_distribution<long long> (l, r)(rng);
}

int n, m, k;
vector<ii> g[N];
int d[N], par[20][N], timedfs = 0, tin[N];
int sum[N];
void DFS(int u) {
    tin[u] = ++timedfs;
    for (auto [v, id]: g[u]) {
        if (v == par[0][u]) continue;
        d[v] = d[u] + 1;
        par[0][v] = u;
        for (int i = 1; i <= 16; i++) {
            par[i][v] = par[i - 1][par[i - 1][v]];
        }
        DFS(v);
    }
}

bool cmp(int a, int b) {
    return tin[a] < tin[b];
}

int LCA(int u, int v) {
    if (u == v) return u;
    if (d[u] < d[v]) swap(u, v);
    int delta = d[u] - d[v];
    for (int i = 0; i <= 16; i++) {
        if (delta & (1 << i)) {
            u = par[i][u];
        }
    }

    if (u == v) return u;

    for (int i = 16; i >= 0; i--) {
        if (par[i][u] != par[i][v]) {
            u = par[i][u];
            v = par[i][v];
        }
    }

    return par[0][u];
}

void up(int u, int v) {
    int lc = LCA(u, v);
  //  cout << u << " " << v << '\n';
    sum[u]++;
    sum[v]++;
    sum[lc] -= 2;
}

vector<int> ans;
void dfs(int u) {
    for (auto [v, id] : g[u]) {
        if (v == par[0][u]) continue;
        dfs(v);
        sum[u] += sum[v];
        if (sum[v] >= 2 * k) ans.push_back(id);
    }
}

int main() {
    ios::sync_with_stdio(0); cin.tie(0);

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

    cin >> n >> m >> k;
    For (i, 1, n - 1) {
        int u, v; cin >> u >> v;
        g[u].push_back({v, i});
        g[v].push_back({u, i});
    }
    memset(d, 0, sizeof d);
    memset(sum ,0, sizeof sum);
    DFS(1);

    For (i, 1, m) {
        int s;
        cin >> s;
        vector<int> spe(s);
        For (j, 1, s) {
            cin >> spe[j - 1];
        }
        sort (all(spe), cmp);
        for (int j = 0; j < s; j++) {
            up(spe[j], spe[(j + 1) % s]);
        }
    }


    dfs(1);
    sort(all(ans));
    cout << ans.size() << '\n';
    for (int x: ans) cout << x << " ";

    cerr << "Time elapsed: " << TIME << " s.\n";
    return 0;
}

Compilation message (stderr)

railway.cpp: In function 'void DFS(int)':
railway.cpp:29:15: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   29 |     for (auto [v, id]: g[u]) {
      |               ^
railway.cpp: In function 'void dfs(int)':
railway.cpp:76:15: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   76 |     for (auto [v, id] : g[u]) {
      |               ^
railway.cpp: In function 'int main()':
railway.cpp:89:17: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   89 |         freopen (".inp", "r", stdin);
      |         ~~~~~~~~^~~~~~~~~~~~~~~~~~~~
railway.cpp:90:17: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   90 |         freopen (".out", "w", stdout);
      |         ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~
railway.cpp:93:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   93 |         freopen(TASK".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
railway.cpp:94:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   94 |         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