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Submission #1044251

# Submission time Handle Problem Language Result Execution time Memory
1044251 2024-08-05T08:22:11 Z 우민규(#11006) Parking (CEOI22_parking) C++17
60 / 100
 189 ms 29840 KB 
#include <bits/stdc++.h>
using namespace std;

int n, m;
vector<int> fst, snd;
// bottom -> up then true, up -> bottom then false
vector<vector<int>> adj;
vector<int> type;
// determine type

vector<bool> visited, is_selfloop;
vector<vector<int>> locs;

enum Component {
    TrivialPath,
    SplitPath,
    PerfectCycle,
    SplitCycle,
    ComplexCycle,
    SelfLoop,
    EmptySelfLoop,
};

// {amt of top, saw path}
pair<int, bool> dfs(int node) {
    visited[node] = true;
    int top_amt = type[node] == 3;
    bool is_path = false;
    for (auto v : adj[node]) {
        if (visited[v]) continue;
        if (v == 0) {
            is_path = true;
        } else {
            auto [tt, ip] = dfs(v);
            top_amt += tt;
            is_path |= ip;
        }
    }
    return {top_amt, is_path};
}

Component component_type(int node) {
    if (is_selfloop[node]) return SelfLoop;

    auto [top_amt, is_path] = dfs(node);
    if (is_path) {
        if (top_amt) return SplitPath;
        return TrivialPath;
    }
    if (top_amt > 1) return ComplexCycle;
    if (top_amt) return SplitCycle;
    return PerfectCycle;
}

vector<pair<int, int>> drives;

vector<int> auxs;

void trivial_contraction(int node) {
    if (node == 0 || type[node] == 3) return;
    int a = locs[node][0];
    int b = locs[node][1];
    if (a == b) return;
    bool can_a_pop = snd[a] == 0 || snd[a] == node;
    bool can_b_pop = snd[b] == 0 || snd[b] == node;
    bool can_a_recv = fst[a] == node && snd[a] == 0;
    bool can_b_recv = fst[b] == node && snd[b] == 0;
    if (can_b_pop && can_a_recv) {
        drives.push_back({b, a});
        fst[a] = snd[a] = node;
        locs[node] = {a, a};
        if (snd[b] == node) {
            snd[b] = 0;
            trivial_contraction(fst[b]);
        } else {
            assert(fst[b] == node);
            fst[b] = 0;
            auxs.push_back(b);
        }
    } else if (can_a_pop && can_b_recv) {
        drives.push_back({a, b});
        fst[b] = snd[b] = node;
        locs[node] = {b, b};
        if (snd[a] == node) {
            snd[a] = 0;
            trivial_contraction(fst[a]);
        } else {
            assert(fst[a] == node);
            fst[a] = 0;
            auxs.push_back(a);
        }
    }
}

void trivial_component_contraction(int node) {
    visited[node] = true;
    trivial_contraction(node);
    for (auto v : adj[node]) {
        if (v == 0 || visited[v]) continue;
        trivial_component_contraction(v);
    }
}

void perfect_cycle_contraction(int node) {
    assert(!auxs.empty());
    int aux = auxs.back();
    auxs.pop_back();
    
    int a = locs[node][0], b = locs[node][1];
    if (snd[a] == node) {
        drives.push_back({a, aux});
        snd[a] = 0;
        fst[aux] = node;
        locs[node][0] = aux;
        trivial_contraction(fst[a]);
    }
    if (snd[b] == node) {
        drives.push_back({b, aux});
        snd[b] = 0;
        fst[aux] = node;
        locs[node][1] = aux;
        trivial_contraction(fst[b]);
    }
}

vector<int> component_top_nodes;
void find_top_node_and_contract_ends(int node) {
    visited[node] = true;
    if (type[node] == 3) component_top_nodes.push_back(node);
    trivial_contraction(node);
    for (auto v : adj[node]) if (v != 0 && !visited[v]) find_top_node_and_contract_ends(v);
}

void with_top_contraction(int node) {
    component_top_nodes.clear();
    find_top_node_and_contract_ends(node);
    for (auto v : component_top_nodes) {
        assert(!auxs.empty());
        int aux = auxs.back();
        auxs.pop_back();

        int a = locs[v][0];
        int b = locs[v][1];
        locs[v][0] = locs[v][1] = aux;

        drives.push_back({a, aux});
        drives.push_back({b, aux});
        snd[a] = 0, snd[b] = 0;
        fst[aux] = snd[aux] = v;
        
        trivial_contraction(fst[a]);
        trivial_contraction(fst[b]);
    }
}


void solve() {
    cin >> n >> m;
    adj.assign(n + 1, {}), type.assign(n + 1, 0), visited.assign(n + 1, false), is_selfloop.assign(n + 1, false);
    locs.assign(n + 1, {});
    int num_type[7]{};
    for (int i = 0; i < m; ++i) {
        int a, b;
        cin >> a >> b;
        if (a) type[a] = 2 * type[a];
        if (b) type[b] = 2 * type[b] + 1;
        fst.push_back(a), snd.push_back(b);
        adj[a].push_back(b), adj[b].push_back(a);
        locs[a].push_back(i), locs[b].push_back(i);
        if (a == 0 && b == 0) {
            num_type[EmptySelfLoop] += 1;
            auxs.push_back(i);
        }
        if (a == b) {
            is_selfloop[a] = true;
        }
    }
    // determine all endpoints
    vector<pair<Component, int>> sources;
    for (int i = 1; i <= n; ++i) {
        if (!visited[i]) {
            Component cur = component_type(i);
            num_type[cur] += 1;
            sources.push_back({cur, i});
        }
    }

    int req_moves = num_type[PerfectCycle];
    for (int i = 1; i <= n; ++i) {
        if (is_selfloop[i]) continue;
        req_moves += 1;
        if (type[i] == 3) req_moves += 1;
    }

    // Check if it's possible
    num_type[EmptySelfLoop] += num_type[TrivialPath];
    num_type[TrivialPath] = 0;
    if (num_type[EmptySelfLoop] == 0 &&
        (num_type[SplitPath] > 0 || num_type[PerfectCycle] > 0 ||
         num_type[SplitCycle] > 0 || num_type[ComplexCycle] > 0)) {
        cout << "-1\n";
        return;
    }
    num_type[EmptySelfLoop] += num_type[SplitPath];
    if (num_type[ComplexCycle] > 0) {
        if (num_type[EmptySelfLoop] < 2) {
            cout << "-1\n";
            return;
        }
    }
    // do the thing
    visited.assign(n + 1, false);
    for (auto [type, idx] : sources) {
        if (type == TrivialPath) trivial_component_contraction(idx);
    }
    for (auto [type, idx] : sources) {
        if (type == SplitPath || type == SplitCycle) with_top_contraction(idx);
        if (type == PerfectCycle) perfect_cycle_contraction(idx);
    }
    for (auto [type, idx] : sources) {
        if (type == ComplexCycle) with_top_contraction(idx);
    }
    // assert(req_moves <= drives.size());
    for (int i = 0; i < m; ++i) {
        assert(fst[i] == snd[i]);
    }
    cout << drives.size() << "\n";
    for (auto [u, v] : drives) cout << u + 1 << " " << v + 1 << "\n";
}

int main() {
    cin.tie(0)->sync_with_stdio(0);
    int t = 1;
    solve();
}

Compilation message

Main.cpp: In function 'int main()':
Main.cpp:233:9: warning: unused variable 't' [-Wunused-variable]
  233 |     int t = 1;
      |         ^

Subtask #1
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 348 KB Output is correct
2 Correct 0 ms 348 KB Output is correct
3 Correct 1 ms 348 KB Output is correct
4 Correct 0 ms 344 KB Output is correct
5 Correct 0 ms 348 KB Output is correct
6 Correct 0 ms 348 KB Output is correct
7 Correct 0 ms 344 KB Output is correct
8 Correct 0 ms 344 KB Output is correct
9 Correct 0 ms 344 KB Output is correct
10 Correct 1 ms 344 KB Output is correct

Subtask #2
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 46 ms 16160 KB Output is correct
2 Correct 60 ms 18600 KB Output is correct
3 Correct 51 ms 13628 KB Output is correct
4 Correct 42 ms 13052 KB Output is correct
5 Correct 62 ms 18600 KB Output is correct

Subtask #3
25.0 / 25.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 348 KB Output is correct
2 Correct 0 ms 344 KB Output is correct
3 Correct 0 ms 348 KB Output is correct
4 Correct 1 ms 856 KB Output is correct
5 Correct 1 ms 344 KB Output is correct
6 Correct 1 ms 348 KB Output is correct
7 Correct 1 ms 604 KB Output is correct
8 Correct 1 ms 348 KB Output is correct
9 Correct 1 ms 600 KB Output is correct

Subtask #4
15.0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 348 KB Output is correct
2 Correct 0 ms 344 KB Output is correct
3 Correct 0 ms 348 KB Output is correct
4 Correct 1 ms 856 KB Output is correct
5 Correct 1 ms 344 KB Output is correct
6 Correct 1 ms 348 KB Output is correct
7 Correct 1 ms 604 KB Output is correct
8 Correct 1 ms 348 KB Output is correct
9 Correct 1 ms 600 KB Output is correct
10 Correct 124 ms 29664 KB Output is correct
11 Correct 63 ms 26044 KB Output is correct
12 Correct 89 ms 23864 KB Output is correct
13 Correct 124 ms 28336 KB Output is correct
14 Correct 77 ms 24636 KB Output is correct
15 Correct 81 ms 23868 KB Output is correct
16 Correct 187 ms 29840 KB Output is correct
17 Correct 96 ms 23612 KB Output is correct
18 Correct 189 ms 29256 KB Output is correct

Subtask #5
0.0 / 25.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 604 KB Output is correct
2 Correct 1 ms 600 KB Output is correct
3 Correct 1 ms 348 KB Output is correct
4 Correct 0 ms 348 KB Output is correct
5 Correct 1 ms 348 KB Output is correct
6 Correct 1 ms 348 KB Output is correct
7 Correct 1 ms 348 KB Output is correct
8 Runtime error 1 ms 860 KB Execution killed with signal 6
9 Halted 0 ms 0 KB -

Subtask #6
0.0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 348 KB Output is correct
2 Correct 0 ms 348 KB Output is correct
3 Correct 1 ms 348 KB Output is correct
4 Correct 0 ms 344 KB Output is correct
5 Correct 0 ms 348 KB Output is correct
6 Correct 0 ms 348 KB Output is correct
7 Correct 0 ms 344 KB Output is correct
8 Correct 0 ms 344 KB Output is correct
9 Correct 0 ms 344 KB Output is correct
10 Correct 1 ms 344 KB Output is correct
11 Correct 46 ms 16160 KB Output is correct
12 Correct 60 ms 18600 KB Output is correct
13 Correct 51 ms 13628 KB Output is correct
14 Correct 42 ms 13052 KB Output is correct
15 Correct 62 ms 18600 KB Output is correct
16 Correct 1 ms 348 KB Output is correct
17 Correct 0 ms 344 KB Output is correct
18 Correct 0 ms 348 KB Output is correct
19 Correct 1 ms 856 KB Output is correct
20 Correct 1 ms 344 KB Output is correct
21 Correct 1 ms 348 KB Output is correct
22 Correct 1 ms 604 KB Output is correct
23 Correct 1 ms 348 KB Output is correct
24 Correct 1 ms 600 KB Output is correct
25 Correct 124 ms 29664 KB Output is correct
26 Correct 63 ms 26044 KB Output is correct
27 Correct 89 ms 23864 KB Output is correct
28 Correct 124 ms 28336 KB Output is correct
29 Correct 77 ms 24636 KB Output is correct
30 Correct 81 ms 23868 KB Output is correct
31 Correct 187 ms 29840 KB Output is correct
32 Correct 96 ms 23612 KB Output is correct
33 Correct 189 ms 29256 KB Output is correct
34 Correct 1 ms 604 KB Output is correct
35 Correct 1 ms 600 KB Output is correct
36 Correct 1 ms 348 KB Output is correct
37 Correct 0 ms 348 KB Output is correct
38 Correct 1 ms 348 KB Output is correct
39 Correct 1 ms 348 KB Output is correct
40 Correct 1 ms 348 KB Output is correct
41 Runtime error 1 ms 860 KB Execution killed with signal 6
42 Halted 0 ms 0 KB -