Submission #1074787

#	Time	Username	Problem	Language	Result	Execution time	Memory
1074787		khanhtb	Bridges (APIO19_bridges)	C++17	0 / 100	3091 ms	7012 KiB

bridges

#include <bits/stdc++.h>
#define ll long long
#define ull unsigned long long
#define ld long double
#define pb push_back
#define pf push_front
#define vi vector<ll>
#define vii vector<vi>
#define pll pair<ll, ll>
#define vpll vector<pll>
#define all(a) a.begin(), a.end()
#define fi first
#define se second
using namespace std;
const int mod = 1e9+7;
const ll inf = 2e18;
const int B = 1e5 + 8;
const int N = 1e5 + 8;
struct DSU_roll_back{
    vector<int> par,sz;
    vector<pair<int &,int>> history;
    void init(int n){
        history.clear();
        par = vector<int> (n+5);
        sz = vector<int> (n+5,1);
        iota(all(par),0);
    }
    int fs(int v){
        return par[v] == v ? v:fs(par[v]);
    }
    void us(int u, int v){
        u = fs(u), v = fs(v);
        if(u == v) return;
        if(sz[u] < sz[v]) swap(u,v);
        history.pb({sz[u],sz[u]});
        history.pb({par[v],par[v]});
        par[v] = u;
        sz[u] += sz[v];
    }
    int now_time(){
        return history.size();
    }
    void roll_back(int time){
        while(now_time() > time){
            history.back().fi = history.back().se;
            history.pop_back();
        }
    }
    int answer(int u){
        return sz[fs(u)];
    }
};

struct query{
    int id,t,v,w;
};
struct edge{
    int u,v,w;
};
vector<edge> ed = {{0,0,0}};
int n,m,q;
vector<query> qr[N/B+2];
int ans[N];
bool mark[N];
int t[N];
void solve(){
    cin >> n >> m;
    DSU_roll_back dsu;
    dsu.init(n);
    for(int i = 1; i <= m; i++){
        int u,v,w;cin >> u >> v >> w;
        ed.pb({u,v,w});
    }
    cin >> q;
    for(int i = 0; i < q; i++){
        int v,w;cin >> t[i] >> v >> w;
        qr[i/B].pb({i,t[i],v,w});
    }
    for(int block = 0; block <= (q-1)/B; block++){
        dsu.roll_back(0);
        vector<edge> unchange;
        for(auto [id,t,v,w]:qr[block]){
            if(t == 1) mark[v] = 1;
        }
        sort(all(qr[block]),[&](query a, query b){
            return a.w > b.w;
        });
        for(int i = 1; i <= m; i++){
            if(!mark[i]) unchange.pb(ed[i]);
        }
        sort(all(unchange),[&](edge a, edge b){
            return a.w < b.w;
        });
        for(int i = 0; i < (int)qr[block].size(); i++){
            auto [id,t,v,w] = qr[block][i];
            while(unchange.size() && unchange.back().w >= w){
                dsu.us(unchange.back().u,unchange.back().v);
                unchange.pop_back();
            }
            if(t == 2){
                map<pair<int,int>,pair<int,int>> join;
                int time = dsu.now_time();
                for(int j = 0; j < (int)qr[block].size(); j++){
                    auto [id1,t1,v1,w1] = qr[block][j];
                    pair<int,int> e = {ed[v1].u,ed[v1].v};
                    if(t1 == 1){
                        if(join.find(e) == join.end()){
                            if(id1 < id) join[e] = {id1,w1};
                            else join[e] = {id1,ed[v1].w};
                        }
                        else{
                            if(id1 < id){
                                if(join[e].fi < id) join[e] = max(join[e],{id1,w1});
                                else join[e] = {id1,w1};
                            }
                            else{
                                if(join[e].fi > id) join[e] = min(join[e],{id1,ed[v1].w});
                            }
                        }
                    } 
                }
                for(auto [u,v]:join) if(v.se >= w){
                    dsu.us(u.fi,u.se);
                    // cout << u.fi << " " << u.se << " " << v.fi << " " << v.se << '\n';
                }
                // cout << '\n';
                ans[id] = dsu.answer(v);
                dsu.roll_back(time);
            }
        }   
        for(auto [id,t,v,w]:qr[block]) if(t == 1) ed[v].w = w, mark[v] = 0;
    }
    for(int i = 0; i < q; i++){
        if(t[i] == 2) cout << ans[i] << '\n';
    }
}
signed main(){
    ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    if (fopen("test.inp", "r")){
        freopen("test.inp", "r", stdin);
        freopen("test.out", "w", stdout);
    }
    int T = 1;
    // cin >> T;
    for (int i = 1; i <= T; i++){
        solve();
        // cout << '\n';
    }
}

Compilation message (stderr)

bridges.cpp: In function 'int main()':
bridges.cpp:140:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  140 |         freopen("test.inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
bridges.cpp:141:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  141 |         freopen("test.out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 13
• Subtask 2: 0 / 16
• Subtask 3: 0 / 17
• Subtask 4: 0 / 14
• Subtask 5: 0 / 13
• Subtask 6: 0 / 27