Submission #922826

#	Time	Username	Problem	Language	Result	Execution time	Memory
922826		asdasdqwer	Railway (BOI17_railway)	C++14	0 / 100	195 ms	80208 KiB

railway

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

#define int int64_t

vector<int> idx;

signed main() {
    int n,m,k;cin>>n>>m>>k;
    vector<vector<int>> g(n);
    for (int i=1;i<n;i++) {
        int a,b;cin>>a>>b;a--;b--;
        g[a].push_back(b);
        g[b].push_back(a);
    }

    idx.assign(n, -1);

    int cnt=0;
    vector<vector<int>> lft(n, vector<int>(20, -1));
    vector<int> d(n);

    function<void(int,int)> dfs=[&](int node,int pv) {
        idx[node]=cnt++;
        for (int x:g[node]) {
            if (x==pv)continue;
            d[x]=d[node]+1;
            lft[x][0]=node;
            dfs(x,node);
        }
    };

    dfs(0, -1);

    for (int j=1;j<20;j++) {
        for (int i=0;i<n;i++) {
            lft[i][j]=lft[i][j-1];
            if (lft[i][j] != -1) {
                lft[i][j] = lft[lft[i][j]][j-1];
            }
        }
    }

    function<int(int,int)> jmp=[&](int a, int steps) -> int {
        int c=0;
        while (steps) {
            if ((steps&1)==1) {
                a=lft[a][c];
            }
            c++;steps>>=1;
        }
        return a;
    };

    function<int(int,int)> lca=[&](int a,int b) -> int {
        if (d[a]<d[b])swap(a,b);
        a=jmp(a,d[a]-d[b]);
        if (a==b)return a;

        for (int i=19;i>=0;i--) {
            if (lft[a][i] != lft[b][i]) {
                a=lft[a][i];
                b=lft[b][i];
            }
        }
        return lft[a][0];
    };

    vector<int> sm(n, 0);

    for (int i=0;i<m;i++) {
        int s;cin>>s;
        vector<int> inp(s);
        for (auto &x:inp){cin>>x;x--;}

        sort(inp.begin(),inp.end(), [](int a, int b) {return idx[a] < idx[b];});

        for (int j=0;j<s;j++) {
            int n1=inp[j];
            int n2=inp[(j+1)%s];
            sm[n1]++;
            sm[n2]++;
            sm[lca(n1,n2)] -= 2;
        }
    }

    function<void(int,int)> dfs2=[&](int node,int pv) {
        for (int x:g[node]) {
            if (x == pv) continue;
            dfs(x,node);
            sm[node] += sm[x];
        }
    };

    dfs2(0, -1);

    vector<int> out;
    for (int i=0;i<n;i++) {
        if (sm[i] >= 2*k) {
            out.push_back(i);
            out.push_back(lft[i][0]);
        }
    }

    sort(out.begin(), out.end());

    vector<int> dis={out[0]};
    for (int x:out) {
        if (dis.back() != x)dis.push_back(x);
    }

    cout<<dis.size()<<"\n";
    for (int x:dis) {
        cout<<x+1<<" ";
    }
    cout<<"\n";
}

• Subtask 1: 0 / 8
• Subtask 2: 0 / 15
• Subtask 3: 0 / 7
• Subtask 4: 0 / 29
• Subtask 5: 0 / 16
• Subtask 6: 0 / 25