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Submission #1044163

# Submission time Handle Problem Language Result Execution time Memory
1044163 2024-08-05T07:43:33 Z 우민규(#11006) Parking (CEOI22_parking) C++17
50 / 100
 135 ms 29880 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 {
            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 {
            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 (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 (!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;
        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());
    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:226:9: warning: unused variable 't' [-Wunused-variable]
  226 |     int t = 1;
      |         ^

Subtask #1
10.0 / 10.0

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

Subtask #2
0.0 / 10.0

# Verdict Execution time Memory Grader output
1 Incorrect 56 ms 15908 KB Output isn't correct
2 Halted 0 ms 0 KB -

Subtask #3
25.0 / 25.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 348 KB Output is correct
2 Correct 1 ms 348 KB Output is correct
3 Correct 1 ms 348 KB Output is correct
4 Correct 1 ms 604 KB Output is correct
5 Correct 0 ms 348 KB Output is correct
6 Correct 0 ms 348 KB Output is correct
7 Correct 1 ms 600 KB Output is correct
8 Correct 0 ms 348 KB Output is correct
9 Correct 1 ms 604 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 1 ms 348 KB Output is correct
3 Correct 1 ms 348 KB Output is correct
4 Correct 1 ms 604 KB Output is correct
5 Correct 0 ms 348 KB Output is correct
6 Correct 0 ms 348 KB Output is correct
7 Correct 1 ms 600 KB Output is correct
8 Correct 0 ms 348 KB Output is correct
9 Correct 1 ms 604 KB Output is correct
10 Correct 128 ms 29684 KB Output is correct
11 Correct 57 ms 26044 KB Output is correct
12 Correct 76 ms 24068 KB Output is correct
13 Correct 133 ms 28348 KB Output is correct
14 Correct 72 ms 24628 KB Output is correct
15 Correct 71 ms 23728 KB Output is correct
16 Correct 133 ms 29880 KB Output is correct
17 Correct 75 ms 23608 KB Output is correct
18 Correct 135 ms 29372 KB Output is correct

Subtask #5
0.0 / 25.0

# Verdict Execution time Memory Grader output
1 Incorrect 0 ms 348 KB Output isn't correct
2 Halted 0 ms 0 KB -

Subtask #6
0.0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 344 KB Output is correct
2 Correct 0 ms 348 KB Output is correct
3 Correct 0 ms 348 KB Output is correct
4 Correct 0 ms 348 KB Output is correct
5 Correct 0 ms 344 KB Output is correct
6 Correct 1 ms 344 KB Output is correct
7 Correct 0 ms 348 KB Output is correct
8 Correct 0 ms 348 KB Output is correct
9 Correct 0 ms 344 KB Output is correct
10 Correct 0 ms 348 KB Output is correct
11 Incorrect 56 ms 15908 KB Output isn't correct
12 Halted 0 ms 0 KB -