Submission #535845

#	Time	Username	Problem	Language	Result	Execution time	Memory
535845		Stickfish	Cat in a tree (BOI17_catinatree)	C++17	100 / 100	136 ms	21876 KiB

catinatree

#include <iostream>
#include <algorithm>
#include <queue>
#include <bitset>
#include <vector>
#include <set>
using namespace std;

const int INF = 1e9;
const int MAXN = 2e5 + 123;
int depth[MAXN];
vector<int> edg[MAXN];
int ans[MAXN];
int mindepth[MAXN];
int sacdepth[MAXN];

int d;

void dfs(int v) {
    //cout << v << endl;
    ans[v] = 1;
    mindepth[v] = depth[v];
    sacdepth[v] = INF;
    for (auto u : edg[v]) {
        depth[u] = depth[v] + 1;
        dfs(u);
        if (mindepth[u] + mindepth[v] - 2 * depth[v] >= d) {
            ans[v] += ans[u];
            sacdepth[v] = min(sacdepth[v], sacdepth[u]);
            mindepth[v] = min(mindepth[v], mindepth[u]);
        } else {
            bool sacv = (mindepth[u] + sacdepth[v] - 2 * depth[v] >= d);
            bool sacu = (mindepth[v] + sacdepth[u] - 2 * depth[v] >= d);
            if (!sacv && !sacu) {
                cout << "ERROR";
                exit(1);
            }
            ans[v] += ans[u] - 1;
            int nmindepth = 0;
            if (sacv) {
                nmindepth = min(mindepth[u], sacdepth[v]);
            }
            if (sacu) {
                nmindepth = max(nmindepth, min(mindepth[v], sacdepth[u]));
            }
            sacdepth[v] = min(sacdepth[v], sacdepth[u]);
            mindepth[v] = nmindepth;
        }
    }
}

signed main() {
    int n;
    cin >> n >> d;
    for (int i = 1; i < n; ++i) {
        int rt;
        cin >> rt;
        edg[rt].push_back(i);
        depth[i] = depth[rt] + 1;
    }
    dfs(0);
    cout << ans[0] << '\n';
}

• Subtask 1: 11 / 11
• Subtask 2: 40 / 40
• Subtask 3: 49 / 49