Submission #1098928

#	Time	Username	Problem	Language	Result	Execution time	Memory
1098928		crafticat	Stranded Far From Home (BOI22_island)	C++17	100 / 100	126 ms	39476 KiB

island

#include <bits/stdc++.h>

#include <utility>

using ll = long long;
using namespace std;
#define F0R(i, n) for (ll i= 0; i < n;i++)
template<typename T>
using V = vector<T>;
using vi = V<ll>;
using vvi = V<vi>;
#define pb push_back
using pi = pair<ll, ll>;
#define all(x) begin(x), end(x)
#define f first
#define s second

V<ll> initSum;

struct dsu {
    vi par, absPar;
    vi siz;
    vi sum;

    dsu(ll n, vi initSum) {
        par.resize(n, -1);
        absPar.resize(n, -1);
        siz.resize(n, 1);
        sum = std::move(initSum);
    }

    ll get(ll x) {
        if (absPar[x] == -1) return x;
        return absPar[x] = get(absPar[x]);
    }

    void combine(ll a, ll b) {
        a = get(a), b = get(b);
        if (a == b) return;

        if (initSum[b] > initSum[a]) swap(a,b);
        siz[a] += siz[b];
        sum[a] += sum[b];
        par[b] = a;
        absPar[b] = a;
    }
};

//TODO CHECK CONNECTIVITY
vvi genGraph(vi par) {
    vvi g(par.size());

    F0R(i, par.size()) {
        if (par[i] == -1) continue;
        g[par[i]].pb(i);
        g[i].pb(par[i]);
    }
    return g;
}
V<bool> possible;
dsu* dsu;
vvi g;

void dfsPos(ll x, ll p) {
    if (p == -1 || dsu->sum[x] >= initSum[p]) possible[x] = true;
    else return;

    for (auto child : g[x]) {
        if (child == p) continue;
        dfsPos(child, x);
    }
}

int main() {
    ios_base::sync_with_stdio(false); cin.tie(nullptr);
    ll n, m; cin >> n >> m;
    V<pair<ll, pi>> edges;
    initSum.resize(n + 1);

    F0R(i, n)
        cin >> initSum[i + 1];

    F0R(i, m) {
        ll a, b; cin >> a>> b;
        edges.pb({max(initSum[a], initSum[b]), {a, b}});
    }

    sort(all(edges));
    dsu = new struct dsu(n + 1, initSum);

    for (auto [x,pa] : edges) {
        auto [a,b] = pa;
        dsu->combine(a,b);
    }

    g = genGraph(dsu->par);
    ll root = dsu->get(1);
    bool pos = true;
    F0R(i, n)
        if (dsu->get(i + 1) != root) pos = false;

    possible.resize(n + 1);

    if (pos) dfsPos(root, -1);
    F0R(i, n) {
        cout << possible[i + 1] << "";
    }

    return 0;
}

Compilation message (stderr)

island.cpp: In function 'vvi genGraph(vi)':
island.cpp:7:35: warning: comparison of integer expressions of different signedness: 'll' {aka 'long long int'} and 'std::vector<long long int, std::allocator<long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
    7 | #define F0R(i, n) for (ll i= 0; i < n;i++)
......
   53 |     F0R(i, par.size()) {
      |         ~~~~~~~~~~~~~              
island.cpp:53:5: note: in expansion of macro 'F0R'
   53 |     F0R(i, par.size()) {
      |     ^~~

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