Submission #1058853

#	Time	Username	Problem	Language	Result	Execution time	Memory
1058853		Pekiban	Ball Machine (BOI13_ballmachine)	C++17	100 / 100	163 ms	28436 KiB

ballmachine

#include <bits/stdc++.h>
 
using namespace std;
#define pb push_back
#define lwb lower_bound
 
const int N = 1e5+5, LOG = 17;
vector<int> g[N];
int up[LOG][N], D[N], mn[N], ps[N];
vector<int> a = {-1};
void dfs1(int s, int e = -1) {
    mn[s] = s;
    for (auto u : g[s]) {
        if (u == e) continue;
        D[u] = D[s] + 1;
        up[0][u] = s;
        dfs1(u, s);
        mn[s] = min(mn[s], mn[u]);
    }
}
bool cmp(int x, int y) {
    return mn[x] < mn[y];
}
void dfs2(int s, int e = -1) {
    sort(g[s].begin(), g[s].end(), cmp);
    for (auto u : g[s]) {
        if (u == e) continue;
        dfs2(u, s);
    }
    a.pb(s);
}
int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    int n, q, R;
    cin >> n >> q;
    for (int i = 1; i <= n; ++i) {
        int p;
        cin >> p;
        if (i == 0) {
            R = i;
            continue;
        }
        g[p].pb(i); g[i].pb(p);
    }
    dfs1(R);
    dfs2(R);
    for (int i = 1; i < LOG; ++i) {
        for (int j = 1; j <= n; ++j) {
            up[i][j] = up[i-1][up[i-1][j]];
        }
    }
    for (int i = 1; i <= n; ++i)    ps[a[i]] = i;
    ps[0] = 1e9;
    set<int> r, av;
    for (int i = 1; i <= n; ++i)    av.insert(i);
    map<int, int> L; L[0] = 1;
    while (q--) {
        int t;
        cin >> t;
        if (t == 1) {
            int k, ans;
            cin >> k;
            while (k--) {
                int x = *av.begin();
                av.erase(x);
                if (r.lwb(x) == r.end() || x+1 < L[*r.lwb(x)]) {
                    L[x] = L[x-1];
                    if (x > 1)  L.erase(x-1);
                    if (x > 1)  r.erase(x-1);
                    r.insert(x);
                }
                else {
                    L[*r.lwb(x)] = L[x-1];
                    if (x > 1)  L.erase(x-1);
                    if (x > 1)  r.erase(x-1);
                }
                ans = x;
            }
            cout << a[ans] << '\n';
        }
        else {
            int x;
            cin >> x;
            int X = x, ri = *r.lwb(ps[x]);
            for (int i = LOG-1; i >= 0; --i) {
                if (ps[up[i][x]] <= ri) x = up[i][x];
            }
            L[ps[x] - 1] = L[ri];
            r.insert(ps[x] - 1);
            if (ps[x] - 1 < L[ps[x] - 1]) {
                L.erase(ps[x] - 1);
                r.erase(ps[x] - 1);
            } 
            L[ri] = ps[x] + 1;
            if (L[ri] > ri) {
                L.erase(ri);
                r.erase(ri);
            }
            av.insert(ps[x]);
            cout << D[X] - D[x] << '\n';
        }
    }
}

Compilation message (stderr)

ballmachine.cpp: In function 'int main()':
ballmachine.cpp:80:26: warning: 'ans' may be used uninitialized in this function [-Wmaybe-uninitialized]
   80 |             cout << a[ans] << '\n';
      |                          ^

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