Submission #217841

#	Time	Username	Problem	Language	Result	Execution time	Memory
217841		lyc	Bridges (APIO19_bridges)	C++14	100 / 100	2880 ms	13408 KiB

bridges

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

#define FOR(i,a,b) for (int i = (a); i <= (b); ++i)
#define SZ(x) ((int)(x).size())
typedef pair<int,int> ii;

const int MX_N = 5e4+5;
const int MX_M = 1e5+5;
const int MX_Q = 1e5+5;
//const int B = 800;
const int B = 500;
//const int B = 230;
//const int B = 1;

struct Edge {
    int s, e, b, w;
};

struct Query {
    int t, s, w;
};

int N, M;
ii bridge[MX_M];
int weight[MX_M];
int time_[MX_M];
int Q;
vector<Edge> edges;
vector<Query> queries;
int ans[MX_Q];

struct UnionFind {
    vector<int> sz, p;
    int history[MX_N], hptr = 0;
    UnionFind(int n) { sz.assign(n,1); p.resize(n); iota(p.begin(),p.end(),0); }
    int findset(int i) { return (p[i] == i) ? i : findset(p[i]); }
    bool unionset(int i, int j) {
        //cout << "union " << i << " " << j << endl;
        int x = findset(i), y = findset(j);
        if (x != y) {
            if (sz[x] > sz[y]) {
                sz[x] += sz[y], p[y] = x;
                history[hptr++] = y;
            } else {
                sz[y] += sz[x], p[x] = y;
                history[hptr++] = x;
            }
            return true;
        } else return false;
    }
    inline int getLoc() { return hptr; }
    inline void undo(int loc) {
        while (hptr > loc) {
            int u = history[--hptr];
            //cout << "undo " << u << " " << p[u] << endl;
            sz[p[u]] -= sz[u], p[u] = u;
        }
    }
    inline int getSize(int i) { return sz[findset(i)]; }
};

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin >> N >> M;
    FOR(i,1,M){
        int U, V, D; cin >> U >> V >> D;
        bridge[i] = {U,V};
        weight[i] = D;
        time_[i] = 0;
    }

    cin >> Q;
    FOR(i,1,Q){
        int T; cin >> T;
        if (T == 1) {
            int B, R; cin >> B >> R;
            edges.emplace_back((Edge){ time_[B],i-1,B,weight[B] });
            time_[B] = i;
            weight[B] = R;

            ans[i] = -1;
        } else {
            int S, W; cin >> S >> W;
            //queries[i/B].emplace_back((Query){ i,S,W });
            queries.emplace_back((Query){ i,S,W });
        }
    }
    FOR(B,1,M){
        edges.emplace_back((Edge){ time_[B],Q+1,B,weight[B] });
    }

    sort(edges.begin(),edges.end(),[](Edge a,Edge b){ return a.w > b.w; });
    sort(queries.begin(),queries.end(),[](Query a,Query b) { if (a.t/B == b.t/B) return a.w > b.w; return a.t < b.t; });
    //for(auto& a : edges) cout << a.s << " " << a.e << " :: " << bridge[a.b].first << " " << bridge[a.b].second << " " << a.w << endl;
    int qi = 0;
    while (qi < SZ(queries)) {
        int b = queries[qi].t/B;
        UnionFind UF(N+1);
        vector<Edge> partial;
        partial.reserve(2*B);
        for (auto& e : edges) {
            if ((e.s >= b*B && e.s <= (b+1)*B-1) || (e.e >= b*B && e.e <= (b+1)*B-1))
                partial.push_back(e);
        }
        //sort(queries[b].begin(),queries[b].end(),[](Query a, Query b){ return a.w > b.w; });
        int fi = 0;
        for (; qi < SZ(queries) && queries[qi].t/B == b; ++qi) {
            Query& q = queries[qi];
            //cout << "BUCKET " << b << " :: " << q.t << " " << q.w << " " << q.s << endl;
            while (fi < SZ(edges) && edges[fi].w >= q.w) {
                //cout << "\tconsider edge " << edges[fi].s << " " << edges[fi].e << " " << bridge[edges[fi].b].first << " " << bridge[edges[fi].b].second << " " << edges[fi].w << endl;
                if (edges[fi].s <= b*B && edges[fi].e >= (b+1)*B-1)
                    UF.unionset(bridge[edges[fi].b].first, bridge[edges[fi].b].second);
                ++fi;
            }
            int loc = UF.getLoc();
            for (auto& e : partial) {
                if (e.s <= q.t && q.t <= e.e && e.w >= q.w) {
                    UF.unionset(bridge[e.b].first, bridge[e.b].second);
                }
            }
            ans[q.t] = UF.getSize(q.s);
            UF.undo(loc);
        }
    }

    FOR(i,1,Q){
        if (ans[i] != -1) cout << ans[i] << '\n';
    }
}

• Subtask 1: 13 / 13
• Subtask 2: 16 / 16
• Subtask 3: 17 / 17
• Subtask 4: 14 / 14
• Subtask 5: 13 / 13
• Subtask 6: 27 / 27