Submission #1013536

#	Time	Username	Problem	Language	Result	Execution time	Memory
1013536		ByeWorld	Railway (BOI17_railway)	C++14	100 / 100	200 ms	48328 KiB

railway

#include <bits/stdc++.h>
#pragma GCC optimize("O3", "unroll-loops")
#define ll long long
#define int long long
#define pb push_back
#define fi first
#define se second
#define lf (id<<1)
#define rg ((id<<1)|1)
#define md ((l+r)>>1)
#define ld long double
using namespace std;
typedef pair<int,int> pii;
typedef pair<pii, int> ipii;
const int MAXN = 2e5+10;
const int MAXA = 2e3+10;
const int INF = 1e18+10;
const int LOG = 19;
const int MOD = 1e9+7;
const int SQRT = 450;
const vector<int> NOL = {};
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const vector<int> dx = {1, -1, 0, 0};
const vector<int> dy = {0, 0, 1, -1};

int n, m, k;
vector <int> adj[MAXN];
int dep[MAXN], anc[MAXN][LOG+5], in[MAXN], tim;
map<pii,int> edge;

void dfs(int nw, int par){
    dep[nw] = dep[par]+1; in[nw] = ++tim;
    anc[nw][0] = par;
    for(auto nx : adj[nw]){
        if(nx==par) continue;
        dfs(nx, nw);
    }
}
int LCA(int x, int y){
    if(dep[x] < dep[y]) swap(x, y);
    for(int i=LOG-1; i>=0; i--){
        if(dep[anc[x][i]] >= dep[y])
            x = anc[x][i];
    }
    if(x == y) return x;
    for(int i=LOG-1; i>=0; i--){
        if(anc[x][i] != anc[y][i]){
            x = anc[x][i]; y = anc[y][i];
        }
    }
    return anc[x][0];
}
int cnt[MAXN];
void OUT(int nw, int par){
    for(auto nx : adj[nw]){
        if(nx==par) continue;
        OUT(nx, nw);
        cnt[nw] += cnt[nx];
    }
}
signed main(){
    cin >> n >> m >> k;
    for(int i=1; i<=n-1; i++){
        int x, y; cin >> x >> y;
        edge[pii(x, y)] = edge[pii(y,x)] = i;
        adj[x].pb(y); adj[y].pb(x);
    }
    dfs(1, 0);

    for(int j=1; j<LOG; j++)
        for(int i=1; i<=n; i++)
            anc[i][j] = anc[ anc[i][j-1] ][j-1];

    for(int i=1; i<=m; i++){
        int num; cin >> num;
        vector <pii> inp;
        for(int xx=1; xx<=num; xx++){
            int x; cin >> x;
            inp.pb({in[x], x});
        }
        sort(inp.begin(), inp.end());

        vector <int> stac;
        for(auto [in, x] : inp){
            if(stac.size() < 2) stac.pb(x);
            else {
                int depba = dep[LCA(stac.back(), x)];
                while(stac.size()>=2 && 
                    dep[ LCA(stac.back(), stac[stac.size()-2]) ] >= depba){
                    int p = stac.back(); stac.pop_back();
                    int q = stac.back(); stac.pop_back();
                    int lca = LCA(p, q);
                    // cout << "upd: " << p << ' ' << q << ' ' << lca << " p\n";
                    cnt[p]++; cnt[q]++; cnt[lca] -= 2;
                    stac.pb(lca);
                }
                stac.pb(x);
            }
        }
        while(stac.size()>=2){
            int p = stac.back(); stac.pop_back();
            int q = stac.back(); stac.pop_back();
            int lca = LCA(p, q);
            // cout << "upd: " << p << ' ' << q << ' ' << lca << " p\n";
            cnt[p]++; cnt[q]++; cnt[lca] -= 2;
            stac.pb(lca);
        }
    }
    // for(int i=1; i<=n; i++) cout << cnt[i] << " p\n";
    OUT(1, 0);
    vector <int> ANS;
    for(int i=1; i<=n; i++){
        if(cnt[i] >= k) ANS.pb(edge[pii(i, anc[i][0]) ]);
    }
    sort(ANS.begin(), ANS.end());
    cout << ANS.size() << '\n';
    for(auto in : ANS) cout << in << ' ';
    cout << '\n';
}

Compilation message (stderr)

railway.cpp: In function 'int main()':
railway.cpp:84:18: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   84 |         for(auto [in, x] : inp){
      |                  ^

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