Submission #589216

#	Time	Username	Problem	Language	Result	Execution time	Memory
589216		Vanilla	Dreaming (IOI13_dreaming)	C++17	47 / 100	115 ms	35820 KiB

dreaming

#include <bits/stdc++.h>
#include "dreaming.h"
typedef long long int64;
using namespace std;
const int maxn = 1e5 + 2;
int64 dp[maxn]; // dp[i] -> max dist to leaf in subtree i
vector <pair <int64, int64> > ad [maxn];
vector <int64> a;
bitset <maxn> vis;

int travelTime(int N, int M, int L, int A[], int B[], int T[]) {
    for (int i = 0; i < M; i++){
        ad[A[i]].push_back({B[i], T[i]});
        ad[B[i]].push_back({A[i], T[i]});
    }
    int64 rs = 0;
    for (int i = 0; i < N; i++){
        if (!vis[i]) {
            auto process = [&] () {
                int64 diam = 0, mxdist = 1e18;

                auto dfs = [&] (int u, auto &&dfs) -> void {
                    vis[u] = 1;
                    for (auto &[v, cost]: ad[u]) {
                        if (!vis[v]) {
                            dfs(v, dfs);
                            dp[u] = max(dp[u], dp[v] + cost);
                        }
                    }
                }; dfs(i, dfs);

                auto sum = [&] (int u, int p, auto &&sum) -> void {
                    vector <int64> sm;
                    for (auto &[v, cost]: ad[u]) {
                        if (v == p) continue;
                        sm.push_back(dp[v] + cost);
                        sum(v, u, sum);
                    }
                    int64 ret = 0;
                    sort(sm.begin(), sm.end(), greater <int64> ());
                    for (int i = 0; i < min(2, (int) sm.size()); i++) ret+=sm[i];
                    diam = max(diam, ret);
                    return;
                }; sum(i, -1, sum);

                auto dist = [&] (int u, int p, int64 pans, auto &&dist) -> void {
                    vector <int64> pref, suff;
                    for (auto &[v, cost]: ad[u]) {
                        if (v == p) continue;
                        pref.push_back(dp[v] + cost);
                        suff.push_back(dp[v] + cost);
                    }
                    for (int i = 1; i < pref.size(); i++) pref[i] = max(pref[i-1], pref[i]);
                    for (int i = suff.size() - 2; i >= 0; i--) suff[i] = max(suff[i + 1], suff[i]);
                    mxdist = min(mxdist, max(pans, suff.empty() ? 0: suff[0]));
                    // cout << u << " " << max(pans, suff.empty() ? 0: suff[0]) << "\n";
                    int idx = 0;
                    for (auto &[v, cost]: ad[u]) {
                        if (v == p) continue;
                        int64 p1 = (idx == 0 ? -1e9 : pref[idx-1]);
                        int64 p2 = (idx == suff.size() - 1 ? -1e9: suff[idx + 1]);
                        dist(v, u, max({p1, p2, pans}) + cost, dist);
                        idx++;
                    }
                }; dist(i, -1, 0, dist);
                rs = max(rs, diam);
                a.push_back(mxdist);
                // cout << i << " " << diam << " " << mxdist << "\n";
            }; process();
        }
    }
    sort(a.begin(), a.end(), greater <int64> ());
    if (a.size() >= 2) rs = max(rs, a[0] + a[1] + L);
    return rs;
}

Compilation message (stderr)

dreaming.cpp: In lambda function:
dreaming.cpp:53:39: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   53 |                     for (int i = 1; i < pref.size(); i++) pref[i] = max(pref[i-1], pref[i]);
      |                                     ~~^~~~~~~~~~~~~
dreaming.cpp: In instantiation of 'travelTime(int, int, int, int*, int*, int*)::<lambda()>::<lambda(int, int, int64, auto:25&&)> [with auto:25 = travelTime(int, int, int, int*, int*, int*)::<lambda()>::<lambda(int, int, int64, auto:25&&)>&; int64 = long long int]':
dreaming.cpp:65:39:   required from here
dreaming.cpp:53:39: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
dreaming.cpp:61:41: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   61 |                         int64 p2 = (idx == suff.size() - 1 ? -1e9: suff[idx + 1]);
      |                                     ~~~~^~~~~~~~~~~~~~~~~~

• Subtask 1: 14 / 14
• Subtask 2: 10 / 10
• Subtask 3: 23 / 23
• Subtask 4: 0 / 18
• Subtask 5: 0 / 12
• Subtask 6: 0 / 23