Submission #729313

#	Time	Username	Problem	Language	Result	Execution time	Memory
729313		colossal_pepe	Dreaming (IOI13_dreaming)	C++17	100 / 100	95 ms	22092 KiB

dreaming

#include "dreaming.h"
#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

const int INF = 1e9;

int n, m, l;
vector<pair<int, int>> dp;
vector<vector<pair<int, int>>> g;

int dfs1(int u, int par, int c, vector<int> &cmp_of) {
    cmp_of[u] = c;
    for (auto [v, w] : g[u]) {
        if (v == par) continue;
        int time = dfs1(v, u, c, cmp_of) + w;
        dp[u] = max(dp[u], max(make_pair(time, dp[u].first), make_pair(dp[u].first, time)));
    }
    return dp[u].first;
}

void dfs2(int u, int par, int c, vector<int> &cmp_of) {
    cmp_of[u] = c;
    for (auto [v, w] : g[u]) {
        if (v == par) continue;
        int time = (dp[u].first != dp[v].first + w ? dp[u].first : dp[u].second) + w;
        dp[v] = max(dp[v], max(make_pair(time, dp[v].first), make_pair(dp[v].first, time)));
        dfs2(v, u, c, cmp_of);
    }
}

int solve() {
    dp.resize(n, {0, 0});
    vector<int> cmp_of(n, -1), longest;
    for (int i = 0; i < n; i++) {
        if (cmp_of[i] == -1) {
            dfs1(i, -1, longest.size(), cmp_of);
            longest.push_back(INF);
        }
    }
    fill(cmp_of.begin(), cmp_of.end(), -1);
    longest.clear();
    int ans = 0;
    for (int i = 0; i < n; i++) {
        if (cmp_of[i] == -1) {
            dfs2(i, -1, longest.size(), cmp_of);
            longest.push_back(INF);
        }
        longest[cmp_of[i]] = min(longest[cmp_of[i]], dp[i].first);
        ans = max(ans, dp[i].first + dp[i].second);
    }
    sort(longest.rbegin(), longest.rend());
    if (longest.size() > 1) ans = max(ans, longest[0] + l + longest[1]);
    if (longest.size() > 2) ans = max(ans, longest[1] + 2 * l + longest[2]);
    return ans;
}

int travelTime(int N, int M, int L, int A[], int B[], int T[]) {
    n = N;
    m = M;
    l = L;
    g.resize(n);
    for (int i = 0; i < m; i++) {
        g[A[i]].push_back({B[i], T[i]});
        g[B[i]].push_back({A[i], T[i]});
    }
    return solve();
}

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