Submission #441817

#	Time	Username	Problem	Language	Result	Execution time	Memory
441817		alan8585	Keys (IOI21_keys)	C++17	9 / 100	163 ms	17260 KiB

keys

#include <vector>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <queue>
using namespace std;

const int MAXN = 3000;
int T, in[MAXN], low[MAXN], instack[MAXN], bs[MAXN];
vector<pair<int, int>> e[MAXN];
vector<pair<int, int>> re[MAXN];
stack<int> st;
vector<vector<int>> SCC;
vector<int> flags;

void dfs(int a) {
    instack[a] = 1;
    st.push(a);
    in[a] = low[a] = ++T;
    for(pair<int, int> i : e[a]) {
        if(!in[i.first]) {
            dfs(i.first);
            low[a] = min(low[a], low[i.first]);
        } else if(instack[i.first]) {
            low[a] = min(low[a], in[i.first]);
        }
    }
    if(in[a] == low[a]) {
        int now = -1;
        SCC.push_back(vector<int>(0));
        do {
            now = st.top();
            bs[now] = (int)SCC.size() - 1;
            st.pop();
            instack[now] = 0;
            SCC.back().push_back(now);
        } while(now != a);
    }
}

int C[MAXN];
int find(int a) {
    if(C[a] == a) return a;
    return C[a] = find(C[a]);
}

vector<set<int>> has_key;
bitset<MAXN> death;
void merge(int a, int b) { //merge a into b
    if(find(a) == find(b)) return;
    a = find(a);
    b = find(b);
    C[a] = b;
    death[a] = 1;
    if(SCC[a].size() > SCC[b].size()) {
        SCC[a].swap(SCC[b]);
        has_key[a].swap(has_key[b]);
    }
    for(int i : SCC[a])
        SCC[b].push_back(i);
    for(int i : has_key[a])
        has_key[b].insert(i);
}

std::vector<int> find_reachable(std::vector<int> r, std::vector<int> u, std::vector<int> v, std::vector<int> c) {
    std::vector<int> ans(r.size(), 0);
    int n = r.size(), m = u.size();
    for(int i = 0; i < m; i++) {
        if(r[u[i]] == c[i])
            e[u[i]].push_back(make_pair(v[i], c[i]));
        if(r[v[i]] == c[i])
            e[v[i]].push_back(make_pair(u[i], c[i]));
    }
    for(int i = 0; i < n; i++) {
        if(!in[i]) {
            dfs(i);
        }
    }

    vector<int> d_in(SCC.size(), 0);
    has_key.resize(SCC.size());
    for(int i = 0; i < (int)SCC.size(); i++)
        for(int j : SCC[i]) {
            has_key[i].insert(r[j]);
            for(pair<int, int> k : e[j])
                if(bs[k.first] != i) {
                    re[bs[k.first]].push_back(make_pair(i, k.second));
                    d_in[i]++;
                }
        }
    queue<int> q;
    for(int i = 0; i < (int)SCC.size(); i++) {
        C[i] = i;
        if(d_in[i] == 0)
            q.push(i);
    }
    // for(int i = 0; i < n; i++) printf("%d %d\n", i, bs[i]);
    while(!q.empty()) {
        int now = q.front(); q.pop();
        for(int x = 0; x < (int)re[now].size(); x++)
        for(pair<int, int> i : re[now]) {
            if(has_key[find(now)].find(i.second) != has_key[find(now)].end())
                merge(now, i.first);//, printf("%d %d\n", now, i.first);
            d_in[i.first]--;
            if(d_in[i.first] == 0)
                q.push(i.first);
        }
    }

    int nmin = MAXN;
    // for(int i = 0; i < n; i++) printf("%d %d\n", i, bs[i]);
    for(int i = 0; i < (int)SCC.size(); i++) {
        bool flag = 0;
        if(C[i] == i) {
            flag = 1;
            for(int j : SCC[i]) {
                // printf("%d\n", j);
                for(pair<int, int> k : e[j]) {
                    // printf("%d %d %d\n", k.first, bs[k.first], i);
                    if(find(bs[k.first]) != i)
                        flag = 0;
                }
            }
        }
        flags.push_back(flag);
        if(flag)
           nmin = min(nmin, (int)SCC[i].size());
    }

    for(int i = 0; i < (int)SCC.size(); i++) {
        if(flags[i] && (int)SCC[i].size() == nmin) {
            for(int j : SCC[i])
                ans[j] = 1;
        }
    }
    return ans;
}

• Subtask 1: 9 / 9
• Subtask 2: 0 / 11
• Subtask 3: 0 / 17
• Subtask 4: 0 / 30
• Subtask 5: 0 / 33