Submission #699738

#	Time	Username	Problem	Language	Result	Execution time	Memory
699738		finn__	Ball Machine (BOI13_ballmachine)	C++17	66.29 / 100	121 ms	53436 KiB

ballmachine

#include <bits/stdc++.h>
using namespace std;

#define N 100000

vector<unsigned> g[N], anc[N];
unsigned min_child[N], postorder[N];
bitset<N> has_ball;

unsigned calc_min_child(unsigned u)
{
    min_child[u] = u;
    for (unsigned const &v : g[u])
        min_child[u] = min(min_child[u], calc_min_child(v));
    return min_child[u];
}

unsigned traverse(unsigned u, vector<unsigned> &path, unsigned i = 0)
{
    for (size_t j = 1; j <= path.size(); j <<= 1)
        anc[u].push_back(path[path.size() - j]);
    path.push_back(u);

    for (unsigned const &v : g[u])
        i = traverse(v, path, i);

    path.pop_back();
    postorder[u] = i++;
    return i;
}

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    size_t n, q;
    cin >> n >> q;
    unsigned r;

    for (size_t i = 0; i < n; i++)
    {
        unsigned p;
        cin >> p;
        if (!p)
            r = i;
        else
            g[p - 1].push_back(i);
    }

    calc_min_child(r);
    for (size_t i = 0; i < n; i++)
        sort(g[i].begin(), g[i].end(), [&](unsigned a, unsigned b)
             { return min_child[a] < min_child[b]; });

    vector<unsigned> path;
    assert(traverse(r, path) == n);

    priority_queue<pair<unsigned, unsigned>> qu;
    for (unsigned i = 0; i < n; i++)
        qu.emplace(n - postorder[i], i);

    while (q--)
    {
        unsigned t, x;
        cin >> t >> x;

        if (t == 1)
        {
            for (size_t i = 0; i < x; i++)
            {
                if (i + 1 == x)
                    cout << qu.top().second + 1 << '\n';
                has_ball[qu.top().second] = 1;
                qu.pop();
            }
        }
        else
        {
            x--;
            assert(has_ball[x]);
            unsigned h = 0;

            for (size_t i = anc[x].size() - 1; i < anc[x].size(); i--)
                if (has_ball[anc[x][i]])
                    x = anc[x][i], h += 1U << i;

            has_ball[x] = 0;
            qu.emplace(n - postorder[x], x);
            cout << h << '\n';
        }
    }
}

Compilation message (stderr)

ballmachine.cpp: In function 'int main()':
ballmachine.cpp:57:20: warning: 'r' may be used uninitialized in this function [-Wmaybe-uninitialized]
   57 |     assert(traverse(r, path) == n);
      |                    ^

• Subtask 1: 19.23076923076923 / 25
• Subtask 2: 30 / 30
• Subtask 3: 14.285714285714286 / 40
• Subtask 4: 2.7777777777777777 / 5