Submission #553910

#	Time	Username	Problem	Language	Result	Execution time	Memory
553910		elazarkoren	Dreaming (IOI13_dreaming)	C++17	100 / 100	89 ms	19464 KiB

dreaming

#include "dreaming.h"
#include <bits/stdc++.h>
#define x first
#define y second
#define all(v) v.begin(), v.end()
#define chkmin(a, b) a = min(a, b)
#define chkmax(a, b) a = max(a, b)
using namespace std;
typedef long long ll;
typedef vector<ll> vi;
typedef vector<vi> vvi;
typedef pair<int, int> pii;
typedef vector<pii> vii;

const int MAX_N = 1e5 + 5;

vii tree[MAX_N];
int deg[MAX_N];

bitset<MAX_N> visited;

pii DfsFar(int node, int parent, int d) {
    visited[node] = true;
    pii p = {d, node};
    for (auto [neighbor, w] : tree[node]) {
        if (neighbor != parent) {
            chkmax(p, DfsFar(neighbor, node, d + w));
        }
    }
    return p;
}

bool DfsPath(int node, int parent, int end, vii &path) {
    if (node == end) {
        path.push_back({node, 0});
        return true;
    }
    for (auto [neighbor, w] : tree[node]) {
        if (neighbor != parent && DfsPath(neighbor, node, end, path)) {
            path.push_back({node, w});
            return true;
        }
    }
    return false;
}

int ans = 0;

pii FindRadius(int node) {
    int v = DfsFar(node, -1, 0).y;
    auto [diameter, u] = DfsFar(v, -1, 0);
    pii x = {diameter, v};
    int dist = 0;
    vii path;
    DfsPath(v, -1, u, path);
    reverse(all(path));
    for (auto [node, w] : path) {
        pii q = {max(dist, diameter - dist), node};
        chkmin(x, q);
        dist += w;
    }
    chkmax(ans, diameter);
    return x;
}

int travelTime(int n, int m, int l, int a[], int b[], int t[]) {
    for (int i = 0; i < m; i++) {
        deg[a[i]]++, deg[b[i]]++;
    }
    for (int i = 0; i < n; i++) {
        tree[i].reserve(deg[i]);
    }
    for (int i = 0; i < m; i++) {
        tree[a[i]].push_back({b[i], t[i]});
        tree[b[i]].push_back({a[i], t[i]});
    }
    vii radius;
    for (int i = 0; i < n; i++) {
        if (!visited[i]) {
            radius.push_back(FindRadius(i));
        }
    }
    sort(all(radius));
    int v = radius.back().y;
    radius.pop_back();
    for (auto [r, node] : radius) {
        tree[v].push_back({node, l});
        tree[node].push_back({v, l});
    }
    return DfsFar(DfsFar(0, -1, 0).y, -1, 0).x;
}

• Subtask 1: 14 / 14
• Subtask 2: 10 / 10
• Subtask 3: 23 / 23
• Subtask 4: 18 / 18
• Subtask 5: 12 / 12
• Subtask 6: 23 / 23