Submission #1040988

#	Time	Username	Problem	Language	Result	Execution time	Memory
1040988		Dan4Life	Fountain Parks (IOI21_parks)	C++17	100 / 100	240 ms	84308 KiB

parks

#include "parks.h"
#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define sz(a) (int)a.size()
#define all(a) begin(a),end(a)
using vi = vector<int>;
using ll = long long;
using ar2 = array<int,2>;
using ar3 = array<int,3>;

const int mxN = (int)2e5+10;
int n;
struct Edge{
    int fa, fb, x, y;
    Edge(int a=0, int b=0, int _x=-1, int _y=-1){
        fa=a, fb=b, x=_x, y=_y;
    }
};
vector<Edge> edges;
vector<ar3> fountains, origFountains;
vector<int> adj[mxN];
set<ar2> usedB, S[mxN];

template<int SZ> struct DSU{
    int p[SZ];
    vector<int> comp[SZ];
    void init(int n){
        for(int i = 0; i < n; i++){
            p[i]=i; comp[i].clear();
            comp[i].pb(i);
        }
    }
    
    int findSet(int i){return p[i]==i?i:p[i]=findSet(p[i]);}
    bool isSameSet(int i, int j) {return findSet(i)==findSet(j);}
    void unionSet(int i, int j){
        adj[i].pb(j); adj[j].pb(i);
        int x = findSet(i), y = findSet(j);
        if(x==y) return;
        if(sz(comp[x]) < sz(comp[y])) swap(x,y);
        p[y]=x; for(auto u : comp[y]) comp[x].pb(u);
    }
    int findSz(int i) { return sz(comp[findSet(i)]); }
};
DSU<mxN> dsu;

int construct_roads(vi x, vi y) {
    n = sz(x); dsu.init(n);
    if (n==1){ build({}, {}, {}, {}); return 1; }
    for(int i = 0; i < n; i++){
        fountains.pb({x[i],y[i],i});
        origFountains.pb({x[i],y[i],i});
    }
    sort(all(fountains),[&](ar3 a, ar3 b){ 
        if(a[0]!=b[0]) return a[0]<b[0];
        return a[1]<b[1]; 
    });
    for(int i = sz(fountains)-1; i>=0; i--)
        S[fountains[i][0]].insert({fountains[i][1], fountains[i][2]});
    for(int i = 1; i < sz(fountains); i++){
        if(fountains[i][0]!=fountains[i-1][0]) continue;
        if(fountains[i][1]-fountains[i-1][1]==2){
            auto [x1,y1,a] = fountains[i-1];
            auto [x2,y2,b] = fountains[i];
            dsu.unionSet(a,b);
        }
    }
    for(int i = 0; i < sz(fountains); i++){
        auto [x1,y1,a] = fountains[i];
        auto itr = S[x1+2].lower_bound({y1,-1});
        if(itr==end(S[x1+2]) or (*itr)[0]!=y1) continue;
        int b = (*itr)[1]; dsu.unionSet(a,b);
    }
    if(dsu.findSz(0)!=n) return 0;
    for(auto [x1,y1,i] : fountains){
        int choice = ((x1+y1)%4==0);
        for(auto j : adj[i]){
            auto [x2,y2,_] = origFountains[j];
            int ver = 0;
            if(x1==x2){
                if(y1>y2) continue;
                ver = 1;
            }
            else if(x1>x2) continue;
            if(choice){
                if(ver){
                    if(!usedB.count({x1+1,y1+1})){
                        usedB.insert({x1+1,y1+1});
                        edges.pb(Edge(i,j,x1+1,y1+1));
                    }
                }
                else{
                    if(!usedB.count({x1+1,y1-1})){
                        usedB.insert({x1+1,y1-1});
                        edges.pb(Edge(i,j,x1+1,y1-1));
                    }
                }
            }
            else{
                if(ver){
                    if(!usedB.count({x1-1,y1+1})){
                        usedB.insert({x1-1,y1+1});
                        edges.pb(Edge(i,j,x1-1,y1+1));
                    }
                }
                else{
                    if(!usedB.count({x1+1,y1+1})){
                        usedB.insert({x1+1,y1+1});
                        edges.pb(Edge(i,j,x1+1,y1+1));
                    }
                }
            }
        }
    }
    vi U, V, A, B;
    for(auto edge : edges){
        U.pb(edge.fa), V.pb(edge.fb);
        A.pb(edge.x), B.pb(edge.y);
    }
    build(U,V,A,B); return 1;
}

• Subtask 1: 5 / 5
• Subtask 2: 10 / 10
• Subtask 3: 15 / 15
• Subtask 4: 20 / 20
• Subtask 5: 20 / 20
• Subtask 6: 30 / 30