Submission #1070596

#	Time	Username	Problem	Language	Result	Execution time	Memory
1070596		thangdz2k7	Circle selection (APIO18_circle_selection)	C++17	100 / 100	1978 ms	78792 KiB

circle_selection

#include <bits/stdc++.h>

using namespace std;

const int N = 3e5 + 5;

long long sqr(long long x){ return x * x; }

struct circle{
    long long x, y, r;

    bool intersect(circle A){
        return sqr(x - A.x) + sqr(y - A.y) <= sqr(r + A.r);
    }
};

int n;
circle a[N];

namespace subtask1{
    int ans[N];

    void solve(){
        while (true){
            long long maxr = 0;
            int idx = 0;
            for (int i = 1; i <= n; ++ i) if (!ans[i] && a[i].r > maxr){
                idx = i;
                maxr = a[i].r;
            }
            if (!idx) break;
            for (int i = 1; i <= n; ++ i) if (!ans[i] && a[idx].intersect(a[i])) ans[i] = idx;
        }
        for (int i = 1; i <= n; ++ i) cout << ans[i] << ' ';
    }
}

vector <int> sr;

namespace subtask2{
    int ans[N];
    set <pair <int, int>> l, r;

    void solve(){
        for (int i = 1; i <= n; ++ i) {
            l.insert({a[i].x - a[i].r, i});
            r.insert({a[i].x + a[i].r, i});
        }

        for (int id : sr){
            if (ans[id]) continue;
            int le = a[id].x - a[id].r;
            int ri = a[id].x + a[id].r;
            auto it = l.lower_bound({le, 0});
            while (it != l.end() && it -> first <= ri){
                int del = it -> second;
                ans[del] = id;
                ++ it;
                l.erase({a[del].x - a[del].r, del});
                r.erase({a[del].x + a[del].r, del});
            }
            it = r.lower_bound({le, 0});
            while (it != r.end() && it -> first <= ri){
                int del = it -> second;
                ans[del] = id;
                ++ it;
                l.erase({a[del].x - a[del].r, del});
                r.erase({a[del].x + a[del].r, del});
            }
        }

        for (int i = 1; i <= n; ++ i) cout << ans[i] << ' ';
    }
}

namespace subtask4{
    using pii = pair <int, int>;

    map <pii, set <int>> grid;
    int ans[N];

    void solve(){
        int radius = a[1].r;
        for (int i = 1; i <= n; ++ i){
            int x = a[i].x / radius;
            int y = a[i].y / radius;
            grid[{x, y}].insert(i);
        }

        for (int id : sr){
            if (ans[id]) continue;
            int x = a[id].x / radius;
            int y = a[id].y / radius;
            for (int i = x - 2; i <= x + 2; ++ i){
                for (int j = y - 2; j <= y + 2; ++ j){
                    auto it1 = grid.find({i, j});
                    if (it1 == grid.end()) continue;
                    for (auto it = (it1 -> second).begin(); it != (it1 -> second).end();){
                        if (a[id].intersect(a[*it])){
                            ans[*it] = id;
                            it = (it1 -> second).erase(it);
                        }
                        else ++ it;
                    }
                }
            }
        }

        for (int i = 1; i <= n; ++ i) cout << ans[i] << ' ';
    }
}

namespace Accepted{
    using pii = pair <int, int>;

    int block = 0, ans[N];
    set <int> remain;
    map <pii, set <int>> grid;

    void recalc(){
        grid.clear();
        for (int id : remain) {
            int x = a[id].x / block;
            int y = a[id].y / block;
            grid[{x, y}].insert(id);
        }
    }

    void solve(){
        for (int i = 1; i <= n; ++ i) remain.insert(i);
        for (int id : sr){
            if (ans[id]) continue;
            if (block == 0 || a[id].r * 2 <= block){
                block = a[id].r;
                recalc();
            }

            int x = a[id].x / block;
            int y = a[id].y / block;
            for (int i = x - 2; i <= x + 2; ++ i){
                for (int j = y - 2; j <= y + 2; ++ j){
                    auto it1 = grid.find({i, j});
                    if (it1 == grid.end()) continue;
                    for (auto it = (it1 -> second).begin(); it != (it1 -> second).end();){
                        if (a[id].intersect(a[*it])){
                            ans[*it] = id;
                            remain.erase(*it);
                            it = (it1 -> second).erase(it);
                        }
                        else ++ it;
                    }
                }
            }
        }

        for (int i = 1; i <= n; ++ i) cout << ans[i] << ' ';
    }
}

void solve(){
    cin >> n;
    bool ck2 = true;
    bool ck4 = true;
    for (int i = 1; i <= n; ++ i) {
        sr.push_back(i);
        cin >> a[i].x >> a[i].y >> a[i].r;
        if (a[i].y != 0) ck2 = false;
        if (i > 1 && a[i].r != a[i - 1].r) ck4 = false;
    }
    sort(sr.begin(), sr.end(), [&](int u, int v){
        if (a[u].r == a[v].r) return u < v;
        return a[u].r > a[v].r;
    });

    if (n <= 5000) subtask1::solve();
    else if (ck2) subtask2::solve();
    else if (ck4) subtask4::solve();
    else Accepted::solve();
}

int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    solve();

    return 0;
}

• Subtask 1: 7 / 7
• Subtask 2: 12 / 12
• Subtask 3: 15 / 15
• Subtask 4: 23 / 23
• Subtask 5: 30 / 30
• Subtask 6: 13 / 13