Submission #723113

#	Time	Username	Problem	Language	Result	Execution time	Memory
723113		dxz05	Stranded Far From Home (BOI22_island)	C++17	100 / 100	516 ms	38992 KiB

island

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
#define all(x) (x).begin(), (x).end()
#define MP make_pair
const int N = 200500;

mt19937 rng(chrono::high_resolution_clock::now().time_since_epoch().count());

int n;
int s[N];
bool can[N];

struct dsu{
    vector<int> p;
    vector<long long> sum;
    vector<set<int>> children;

    dsu(){
        p.resize(n);
        iota(all(p), 0);

        sum.resize(n);
        for (int i = 0; i < n; i++) sum[i] = s[i];

        children.resize(n);
        for (int i = 0; i < n; i++){
            children[i].insert(i);
        }
    }

    int leader(int x){
        return (x == p[x] ? x : p[x] = leader(p[x]));
    }

    bool unite(int x, int y){
        int px = leader(x);
        int py = leader(y);
        if (px == py) return false;

        if (sum[px] < s[y]){
            for (int i : children[px]) can[i] = false;
            children[px].clear();
        }
        if (sum[py] < s[x]){
            for (int i : children[py]) can[i] = false;
            children[py].clear();
        }

        x = px, y = py;

        if (children[x].size() > children[y].size()) swap(x, y);

        for (int i : children[x]) children[y].insert(i);
        children[x].clear();

        sum[y] += sum[x];
        p[x] = y;

        return true;
    }
};

vector<int> g[N];
void solve(){
    int m;
    cin >> n >> m;

    for (int i = 0; i < n; i++){
        cin >> s[i];
    }

    vector<pair<int, int>> edges;
    while (m--){
        int u, v;
        cin >> u >> v;
        --u, --v;
        g[u].push_back(v);
        g[v].push_back(u);
        if (s[u] > s[v]) swap(u, v);
        edges.emplace_back(u, v);
    }

    sort(all(edges), [](auto x, auto y){
        return s[x.second] < s[y.second];
    });

    fill(can, can + n, true);

    dsu d;
    for (auto [u, v] : edges){
        d.unite(u, v);
    }

    for (int i = 0; i < n; i++){
        cout << can[i];
    }

}

int main() {
    ios_base::sync_with_stdio(false);

#ifdef LOCAL
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif

    solve();

    return 0;
}

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 15 / 15
• Subtask 4: 30 / 30
• Subtask 5: 35 / 35