Submission #589274

#	Time	Username	Problem	Language	Result	Execution time	Memory
589274		Vanilla	Dreaming (IOI13_dreaming)	C++17	100 / 100	163 ms	35852 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 <pair <int64, 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;
    int64 diam = 0, mxdist = 1e15;
    int wh = 0;
    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);
            }
        }
    }; 
    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;
    }; 
    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]);
        if (max(pans, suff.empty() ? 0: suff[0]) < mxdist) {
            mxdist = max(pans, suff.empty() ? 0: suff[0]);
            wh = u;
        }
        int idx = 0;
        for (auto &[v, cost]: ad[u]) {
            if (v == p) continue;
            int64 p1 = (idx == 0 ? -1e15 : pref[idx-1]);
            int64 p2 = (idx == suff.size() - 1 ? -1e15: suff[idx + 1]);
            dist(v, u, max({p1, p2, pans}) + cost, dist);
            idx++;
        }
    }; 
    for (int i = 0; i < N; i++){
        if (!vis[i]) {
            auto process = [&] () {
                diam = 0, mxdist = 1e15;
                wh = 0;
                dfs(i, dfs);
                sum(i, -1, sum);
                dist(i, -1, 0, dist);
                rs = max(rs, diam);
                a.push_back({mxdist, wh});
            }; process();
        }
    }
    sort(a.begin(), a.end(), greater <pair <int64, int64>> ());
    for (int i = 1; i < a.size(); i++){
        ad[a[0].second].push_back({a[i].second, L});
        ad[a[i].second].push_back({a[0].second, L});
    }
    diam = 0;
    for (int i = 0; i < N; i++){
        dp[i] = 0;
    }
    vis = 0;
    dfs(1, dfs);
    sum(1, -1, sum);
    return diam;
}

Compilation message (stderr)

dreaming.cpp: In lambda function:
dreaming.cpp:48:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   48 |         for (int i = 1; i < pref.size(); i++) pref[i] = max(pref[i-1], pref[i]);
      |                         ~~^~~~~~~~~~~~~
dreaming.cpp: In function 'int travelTime(int, int, int, int*, int*, int*)':
dreaming.cpp:77:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   77 |     for (int i = 1; i < a.size(); i++){
      |                     ~~^~~~~~~~~~
dreaming.cpp: In instantiation of 'travelTime(int, int, int, int*, int*, int*)::<lambda(int, int, int64, auto:25&&)> [with auto:25 = travelTime(int, int, int, int*, int*, int*)::<lambda(int, int, int64, auto:25&&)>&; int64 = long long int]':
dreaming.cpp:70:36:   required from here
dreaming.cpp:48:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   48 |         for (int i = 1; i < pref.size(); i++) pref[i] = max(pref[i-1], pref[i]);
      |                         ~~^~~~~~~~~~~~~
dreaming.cpp:58:29: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   58 |             int64 p2 = (idx == suff.size() - 1 ? -1e15: suff[idx + 1]);
      |                         ~~~~^~~~~~~~~~~~~~~~~~

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