Submission #1264424

#	Time	Username	Problem	Language	Result	Execution time	Memory
1264424		Art	Parachute rings (IOI12_rings)	C++20	100 / 100	680 ms	94184 KiB

rings

//      - Art -
#include <bits/stdc++.h>

#define el              cout << '\n'

#define FOR(i, a, b)    for (int i = (a), _b = (b); i <= _b; ++i)
#define REV(i, b, a)    for (int i = (b), _a = (a); i >= _a; --i)
#define REP(i, c)       for (int i = 0, _c = (c); i < _c; ++i)

const int N = 1e6 + 7;

using namespace std;

struct DisjointSet {
    vector<int> lab;

    DisjointSet(int n = 0) {
        lab.assign(n + 1, -1);
    }

    int findSet(int x) {
        return lab[x] < 0 ? x : lab[x] = findSet(lab[x]);
    }

    bool unionSet(int x, int y) {
        x = findSet(x), y = findSet(y);
        if (x == y) {
            return false;
        }
        if (lab[x] > lab[y]) swap(x, y);
        lab[x] += lab[y];
        lab[y] = x;
        return true;
    }

    int getSize(int x) {
        return -lab[findSet(x)];
    }
};

struct Graph {
    vector<int> deg;
    int n, delNode;
    int szCycle; // 0 = no cycle, -1 = more than one cycle
    bool deg3;
    DisjointSet dsu;

    Graph() {
        n = delNode = szCycle = 0;
        deg3 = false;
    }
    Graph(int _n, int _delNode) {
        n = _n;
        delNode = _delNode;
        szCycle = 0;
        deg3 = false;
        deg.assign(n + 1, 0);
        dsu = DisjointSet(n);
    }

    void addEdge(int u, int v) {
        if (u == delNode || v == delNode) {
            return;
        }
        if (++deg[u] >= 3) {
            deg3 = true;
        }
        if (++deg[v] >= 3) {
            deg3 = true;
        }

        if (!dsu.unionSet(u, v)) { // u, v already in same set
            int sz = dsu.getSize(u);
            if (szCycle == 0) {
                szCycle = sz;
            }
            else {
                szCycle = -1;
            }
        }
    }

    bool isValid() {
        return !deg3 && !szCycle;
    }

    int calc() {
        if (szCycle == -1) {
            return 0;
        }
        return !szCycle ? n : szCycle;
    }
} whole, rem[4];

int n;
vector<int> adj[N];
int pharse = 1;

void Init(int _n) {
    n = _n;
    whole = Graph(_n, -1);
}

void Link(int u, int v) {
    ++u; ++v;
    adj[u].emplace_back(v);
    adj[v].emplace_back(u);

    if (pharse == 1) {
        if (adj[u].size() == 3 || adj[v].size() == 3) {
            int tmp = adj[u].size() == 3 ? u : v;
            rem[0] = Graph(n, tmp);
            rem[1] = Graph(n, adj[tmp][0]);
            rem[2] = Graph(n, adj[tmp][1]);
            rem[3] = Graph(n, adj[tmp][2]);
            FOR (u, 1, n) for (int &v : adj[u]) if (u < v) {
                REP (i, 4) {
                    rem[i].addEdge(u, v);
                }
            }
            pharse = 2;
        }
        else {
            whole.addEdge(u, v);
        }
    }
    else {
        REP (i, 4) {
            rem[i].addEdge(u, v);
        }
    }
}

int CountCritical() {
    if (pharse == 1) {
        return whole.calc();
    }
    int res = 0;
    REP (i, 4) {
        res += rem[i].isValid();
    }
    return res;
}

#ifdef ONLINE_JUDGE
int main() {

    #define name "art"
    if (fopen(name".inp", "r")) {
        freopen(name".inp", "r", stdin);
        freopen(name".out", "w", stdout);
    }

    ios_base::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);

//    int subtask;
//    cin >> subtask;

    int n, q;
    cin >> n >> q;
    Init(n);
    FOR (i, 1, q) {
        int u, v;
        cin >> u;
        if (u == -1) {
            cout << CountCritical(), el;
        }
        else {
            cin >> v;
            Link(u, v);
        }
    }

    return 0;
}
#endif // ONLINE_JUDGE

• Subtask 1: 20 / 20
• Subtask 2: 17 / 17
• Subtask 3: 18 / 18
• Subtask 4: 14 / 14
• Subtask 5: 31 / 31