Submission #565399

#	Time	Username	Problem	Language	Result	Execution time	Memory
565399		shrimb	Building Skyscrapers (CEOI19_skyscrapers)	C++17	51 / 100	3573 ms	46796 KiB

skyscrapers

#pragma GCC optimize ("Ofast")
#pragma GCC target ("avx,avx2,fma")

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

#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;

template<class x>
using ordered_set = tree<x, null_type,less<x>, rb_tree_tag,tree_order_statistics_node_update>;

// #define int long long
#define endl '\n'
#define mod 1000000007
//\
#define mod 1686876991

#define MN -1000000001

const int maxn = 150001;
const int dx[] = {-1, 1, 0, 0, 1, 1, -1, -1};
const int dy[] = {0, 0, 1, -1, -1, 1, -1, 1};
//
const int roundx[] = {1, 1, 0, -1, -1, -1, 0, 1, 1};
const int roundy[] = {0, 1, 1, 1, 0, -1, -1, -1, 0};

struct cell {int x, y, id;};
int n, t, ID = 0, buf;
int x[maxn], y[maxn];
cell cells[maxn];
int dsu[4 * maxn];
vector<pair<int,int>> vec[4 * maxn];
bool out[4 * maxn];
pair<int,int> mp[4 * maxn];

unordered_map<int,unordered_map<int,int>> Empty, Full; // maps cell to dsu
set<cell> active, expendable;

bool operator < (const cell& a, const cell& b) {
    return a.id > b.id;
}

int Find (int x) {
    return dsu[x] == x ? x : dsu[x] = Find(dsu[x]);
}

void check (const cell &c) {
    auto [u, v, id] = c;
    int prev = -1;
    bool artic = 0, sep = 0;
    vector<int> to_reset;
    for (int w = 0 ; w < 9 ; w++) {
        int d = w%8;
        int u2 = u + roundx[d];
        int v2 = v + roundy[d];
        if (Full.count(u2) and Full[u2].count(v2)) sep = 1;
        else {
            if (d & 1) {
                continue;
            }
            int cmp = Find(Empty[u2][v2]);
            if (mp[cmp].first != MN and sep == 1) {
                auto [pu, pv] = mp[cmp];
                bool bad = 0;
                for (int ww = w ; ; ww++) {
                    int d2 = ww % 8;
                    int u3 = u + roundx[d2];
                    int v3 = v + roundy[d2];
                    if (u3 == pu and v3 == pv) {
                        break;
                    }
                    else {
                        if (Full.count(u3) and Full[u3].count(v3)) {
                            bad = 1;
                            break;
                        }
                    }
                }
                if (bad) artic = 1;
            }
            mp[cmp] = {u2, v2};
            to_reset.push_back(cmp);
            sep = 0;
            prev = cmp;
        }
    }

    for (int cmp : to_reset) {
        mp[cmp] = {MN,-1};
    }
    bool isout = 0;
    if (!artic) {
        for (int d = 0 ; d < 4 ; d++) {
            int u2 = u + dx[d];
            int v2 = v + dy[d];
            if (Empty[u2].count(v2)) {
                int cmp = Find(Empty[u2][v2]);
                if (out[cmp]) isout = 1;
            }
        }
    }
    if (isout and !artic) expendable.insert(c);
    else expendable.erase(c);
}


void Union (int a, int b) {
    int x = Find(a), y = Find(b);
    if (x == y) return;
    if (vec[x].size() < vec[y].size()) {
        out[y] |= out[x];
        dsu[x] = y;
        for (auto [u, v] : vec[x]) {
            vec[y].push_back({u, v});
            for (int d = 0 ; d < 8 ; d++) {
                if (Full[u + dx[d]].count(v + dy[d])) check(cells[Full[u + dx[d]][v + dy[d]]]);
            }
        }
        vec[x].clear();
    } else {
        out[x] |= out[y];
        dsu[y] = x;
        for (auto [u, v] : vec[y]) {
            vec[x].push_back({u, v});
            for (int d = 0 ; d < 8 ; d++) {
                if (Full[u + dx[d]].count(v + dy[d])) check(cells[Full[u + dx[d]][v + dy[d]]]);
            }
        }
        vec[y].clear();
    }
}

signed main () {
    cin.tie(0)->sync_with_stdio(0);
    cin >> n >> t;
    for (auto& [i, j] : mp) i = j = MN;

    for (int i = 0 ; i < n ; i++) {
        cin >> x[i] >> y[i];
        cells[i] = {x[i], y[i], i};
        Full[x[i]][y[i]] = i;
        active.insert(cells[i]);
    }

    if (n > 1) {
        for (int i = 0 ; i < n ; i++) {
            bool good = 0;
            for (int d = 0 ; d < 8 ; d++) {
                int u = x[i] + dx[d];
                int v = y[i] + dy[d];
                good |= Full[u].count(v);
            }
            if (!good) {
                cout << "NO\n";
                return 0;
            }
        }
    }

    /* set at leat one node as out (for reference) */ {
        pair<int,int> mn = {x[0], y[0]};

        for (int i = 0 ; i < n ; i++) {
            mn = min(mn, {x[i], y[i]});
        }
        auto [u, v] = mn; u--;
        int id = Empty[u][v] = ID++;
        dsu[id] = id;
        vec[id].push_back({u, v});
        out[id] = 1;
    }

    for (int i = 0 ; i < n ; i++) {
        for (int d = 0 ; d < 8 ; d++) {
            int u = x[i] + dx[d];
            int v = y[i] + dy[d];
            if (!Full[u].count(v) and !Empty[u].count(v)) {
                int id = Empty[u][v] = ID++;
                dsu[id] = id;
                vec[id].push_back({u, v});
            }
        }
    }

    for (int i = 0 ; i < n ; i++) {
        for (int d = 0 ; d < 8 ; d++) {
            int u = x[i] + dx[d];
            int v = y[i] + dy[d];
            if (!Full[u].count(v)) {
                for (int d2 = 0 ; d2 < 4 ; d2++) {
                    int u2 = u + dx[d2];
                    int v2 = v + dy[d2];
                    if (Empty[u2].count(v2)) {
                        Union(Empty[u][v], Empty[u2][v2]);
                    }
                }
            }
        }
    }

    for (int i = 0 ; i < n ; i++) check(cells[i]);

    cout << "YES\n";

    vector<int> ans;

    while (expendable.size()) {
        auto [a, b, c] = *expendable.begin();
        expendable.erase(expendable.begin());
        ans.push_back(c + 1);
        Full[a].erase(b);
        int id = Empty[a][b] = ID++;
        dsu[id] = id;
        vec[id].push_back({a, b});
        for (int d = 0 ; d < 4 ; d++) {
            int u = a + dx[d];
            int v = b + dy[d];
            if (!Full[u].count(v) and !Empty[u].count(v)) {
                assert(0);
                int id = Empty[u][v] = ID++;
                dsu[id] = id;
                vec[id].push_back({u, v});
            }
            if (Empty[u].count(v)) {
                Union(Empty[u][v], id);
            }
        }
        for (int d = 0 ; d < 8 ; d++) {
            int u = a + dx[d];
            int v = b + dy[d];
            if (Full[u].count(v)) check(cells[Full[u][v]]);
        }
    }

    reverse(ans.begin(), ans.end());

    for (int i : ans) cout << i << "\n";
}

Compilation message (stderr)

skyscrapers.cpp:17:1: warning: multi-line comment [-Wcomment]
   17 | //\
      | ^
skyscrapers.cpp: In function 'void check(const cell&)':
skyscrapers.cpp:51:9: warning: variable 'prev' set but not used [-Wunused-but-set-variable]
   51 |     int prev = -1;
      |         ^~~~

• Subtask 1: 8 / 8
• Subtask 2: 14 / 14
• Subtask 3: 12 / 12
• Subtask 4: 17 / 17
• Subtask 5: 0 / 20
• Subtask 6: 0 / 10
• Subtask 7: 0 / 19