Submission #1047930

#	Time	Username	Problem	Language	Result	Execution time	Memory
1047930		ortsac	Ball Machine (BOI13_ballmachine)	C++17	4.84 / 100	154 ms	23380 KiB

ballmachine

#include <bits/stdc++.h>

using namespace std;

const int MAXN = 1e5 + 10;
int cont = 0;
int in[MAXN], out[MAXN], dad[MAXN];
int within[MAXN];
vector<int> adj[MAXN];

void dfs(int node) {
    in[node] = ++cont;
    within[cont] = node;
    for (auto u : adj[node]) {
        if (u != dad[node]) dfs(u);
    }
    out[node] = cont;
}

struct Node {
    bool ocupado = 1;
    int mil = 0x3f3f3f3f;
};

Node merge(Node a, Node b) {
    Node ans;
    ans.ocupado = (a.ocupado && b.ocupado);
    ans.mil = min(a.mil, b.mil);
    return ans;
}

Node seg[4*MAXN];

void build(int node, int l, int r) {
    if (l == r) {
        seg[node].ocupado = 0;
        seg[node].mil = within[l];
        return;
    }
    int m = (l + r)/2;
    build(2*node, l, m);
    build(2*node + 1, m + 1, r);
    seg[node] = merge(seg[2*node], seg[2*node + 1]);
}

Node empt;

Node query(int node, int l, int r, int tl, int tr) {
    if ((l > tr) || (tl > r)) return empt;
    if ((tl <= l) && (r <= tr)) return seg[node];
    int m = (l + r)/2;
    return merge(query(2*node, l, m, tl, tr), query(2*node + 1, m + 1, r, tl, tr));
}

void update(int node, int l, int r, int po, bool v) {
    if (l == r) {
        seg[node].ocupado = v;
        if (v) seg[node].mil = 0x3f3f3f3f;
        else seg[node].mil = within[l];
        return;
    }
    int m = (l + r)/2;
    if (po <= m) {
        update(2*node, l, m, po, v);
    } else {
        update(2*node + 1, m + 1, r, po, v);
    }
    seg[node] = merge(seg[2*node], seg[2*node + 1]);
}

int main() {
    int n, q;
    cin >> n >> q;
    int root;
    for (int i = 1; i <= n; i++) {
        cin >> dad[i];
        adj[dad[i]].push_back(i);
        if (dad[i] == 0) root = i;
    }
    dfs(root);
    build(1, 1, n);
    while (q--) {
        int t, x;
        cin >> t >> x;
        if (t == 2) {
            update(1, 1, n, in[x], 0);
            cout << "0\n";
            continue;
        }
        auto k = query(1, 1, n, in[x], out[x]).mil;
        cout << k << "\n";
        update(1, 1, n, in[k], 1);
    }
}

Compilation message (stderr)

ballmachine.cpp: In function 'int main()':
ballmachine.cpp:80:8: warning: 'root' may be used uninitialized in this function [-Wmaybe-uninitialized]
   80 |     dfs(root);
      |     ~~~^~~~~~

• Subtask 1: 0 / 25
• Subtask 2: 4.285714285714286 / 30
• Subtask 3: 0 / 40
• Subtask 4: 0.5555555555555556 / 5