Submission #1113813

#	Time	Username	Problem	Language	Result	Execution time	Memory
1113813		_callmelucian	Torrent (COI16_torrent)	C++14	100 / 100	320 ms	46072 KiB

torrent

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

typedef long long ll;
typedef long double ld;
typedef pair<ll,ll> pl;
typedef pair<int,int> pii;
typedef tuple<int,int,int> tpl;

#define all(a) a.begin(), a.end()
#define filter(a) a.erase(unique(all(a)), a.end())

const int mn = 3e5 + 5;
int up[mn][19];
vector<int> adj[mn];

void preDfs (int u, int p) {
    up[u][0] = p;
    for (int i = 1; i < 19; i++)
        up[u][i] = up[up[u][i - 1]][i - 1];
    for (int v : adj[u])
        if (v != p) preDfs(v, u);
}

int solve (int u, int p, int block) {
    vector<int> line;
    for (int v : adj[u])
        if (v != p && v != block) line.push_back(solve(v, u, block));
    sort(all(line), greater<int>());

    int ans = 0;
    for (int i = 0; i < line.size(); i++) ans = max(ans, line[i] + i + 1);
    return ans;
}

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

    int n, u, v; cin >> n >> u >> v;
    for (int i = 1; i < n; i++) {
        int a, b; cin >> a >> b;
        adj[a].push_back(b);
        adj[b].push_back(a);
    }
    preDfs(u, u);

    int ans = max(solve(u, u, v), solve(v, v, up[v][0])), optNode = v;
    for (int i = 18; i >= 0; i--) {
        if (up[optNode][i] == u) continue;
        int tmp = up[optNode][i], calcU = solve(u, u, tmp), calcV = solve(v, v, up[tmp][0]);
        if (calcU >= calcV)
            optNode = tmp, ans = max(calcU, calcV);
    }

    if (up[optNode][0] != u)
        ans = min(ans, max(solve(u, u, up[optNode][0]), solve(v, v, up[optNode][1])));
    cout << ans;

    return 0;
}

Compilation message (stderr)

torrent.cpp: In function 'int solve(int, int, int)':
torrent.cpp:32:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   32 |     for (int i = 0; i < line.size(); i++) ans = max(ans, line[i] + i + 1);
      |                     ~~^~~~~~~~~~~~~

• Subtask 1: 31 / 31
• Subtask 2: 69 / 69