Submission #802179

#	Time	Username	Problem	Language	Result	Execution time	Memory
802179		borisAngelov	Dreaming (IOI13_dreaming)	C++17	100 / 100	53 ms	17116 KiB

dreaming

#include "dreaming.h"
#include <bits/stdc++.h>

using namespace std;

const int maxn = 100005;

int n, m;

vector<pair<int, int>> g[maxn];

long long dp[maxn];
bool visited[maxn];

void dfs_down(int node, int par)
{
    visited[node] = true;
    dp[node] = 0;

    for (int i = 0; i < g[node].size(); ++i)
    {
        if (g[node][i].first != par)
        {
            dfs_down(g[node][i].first, node);
            dp[node] = max(dp[node], g[node][i].second + dp[g[node][i].first]);
        }
    }
}

long long longest = 0;

long long dfs_up(int node, int par, long long up)
{
    long long result = max(up, dp[node]);
    longest = max(longest, dp[node] + up);

    long long max1 = 0;
    long long max2 = 0;

    for (int i = 0; i < g[node].size(); ++i)
    {
        int child = g[node][i].first;
        int edge = g[node][i].second;

        if (child == par)
        {
            continue;
        }

        if (dp[child] + edge > max1)
        {
            max2 = max1;
            max1 = dp[child] + edge;
        }
        else if (dp[child] + edge > max2)
        {
            max2 = dp[child] + edge;
        }
    }

    for (int i = 0; i < g[node].size(); ++i)
    {
        if (g[node][i].first == par)
        {
            continue;
        }

        int child = g[node][i].first;
        int edge = g[node][i].second;

        long long new_up = 0;

        if (dp[child] + edge == max1)
        {
            new_up = max(up, max2) + edge;
        }
        else
        {
            new_up = max(up, max1) + edge;
        }

        result = min(result, dfs_up(child, node, new_up));
    }

    return result;
}

int travelTime(int N, int M, int L, int A[], int B[], int T[])
{
    n = N;
    m = M;

    for (int i = 0; i < m; ++i)
    {
        int x = A[i] + 1;
        int y = B[i] + 1;
        int w = T[i];

        g[x].push_back(make_pair(y, w));
        g[y].push_back(make_pair(x, w));
    }

    vector<long long> dists;

    for (int i = 1; i <= n; ++i)
    {
        if (visited[i] == false)
        {
            dfs_down(i, -1);
            dists.push_back(dfs_up(i, -1, 0));
        }
    }

    sort(dists.begin(), dists.end());

    if (dists.size() == 1)
    {
        return max(longest, dists[0]);
    }

    long long ans = max(longest, dists[dists.size() - 1] + dists[dists.size() - 2] + L);

    if (dists.size() >= 3)
    {
        ans = max(ans, dists[dists.size() - 2] + dists[dists.size() - 3] + 2 * L);
    }

    return ans;
}

/*int main()
{
    int A[8] = {0, 8, 2, 5, 5, 1, 1, 10};
    int B[8] = {8, 2, 7, 11, 1, 3, 9, 6};
    int T[8] = {4, 2, 4, 3, 7, 1, 5, 3};

    std::cout << travelTime(12, 8, 2, A, B, T) << std::endl;

    return 0;
}*/

Compilation message (stderr)

dreaming.cpp: In function 'void dfs_down(int, int)':
dreaming.cpp:20:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   20 |     for (int i = 0; i < g[node].size(); ++i)
      |                     ~~^~~~~~~~~~~~~~~~
dreaming.cpp: In function 'long long int dfs_up(int, int, long long int)':
dreaming.cpp:40:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   40 |     for (int i = 0; i < g[node].size(); ++i)
      |                     ~~^~~~~~~~~~~~~~~~
dreaming.cpp:61:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   61 |     for (int i = 0; i < g[node].size(); ++i)
      |                     ~~^~~~~~~~~~~~~~~~

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