Submission #1011962

#	Time	Username	Problem	Language	Result	Execution time	Memory
1011962		andrei_iorgulescu	Beads and wires (APIO14_beads)	C++14	100 / 100	174 ms	80936 KiB

beads

#include <bits/stdc++.h>

using namespace std;

#define int long long

int inf = 2e9;

int root;
int n;
vector<pair<int,int>> g[200005], f[200005];
pair<int,int> t[200005];
int dp[200005][2][2];

/**
Conditii:
- muchiile albastre sa fie de forma 2k
- pot alege k noduri si sa dau fiecaruia doua muchii albastre din set, pe care le voi orienta spre nodul respectiv
- sa nu existe doua noduri din cele k, astfel incat fiecare muchie din cele 4 orientate spre vreun nod din astea "se uita" si spre celalalt

Deci am un dp[nod][0/1][0/1] care reprezinta: suma costurilor max cu care pot face subarb lui nod, folosesc sau nu muchia nod--t[nod],
am sau nu am vreun nod albastru in subarbore pentru care ambele muchii care se uita spre el sa ii vina din fii?
**/

void dfs(int nod)
{
    for (auto vecin : g[nod])
    {
        if (vecin.first != t[nod].first)
        {
            f[nod].push_back(vecin);
            t[vecin.first] = {nod,vecin.second};
            dfs(vecin.first);
        }
    }
}

/*
10
4 10 2
1 2 21
1 3 13
6 7 1
7 9 5
2 4 3
2 5 8
1 6 55
6 8 34
*/

void solve(int nod)
{
    if (f[nod].empty())
    {
        dp[nod][0][0] = 0;
        dp[nod][0][1] = dp[nod][1][0] = dp[nod][1][1] = -inf;
        return;
    }
    for (auto vecin : f[nod])
        solve(vecin.first);
    for (int j = 0; j < 2; j++)
        for (int q = 0; q < 2; q++)
            dp[nod][j][q] = -inf;
    dp[nod][0][0] = 0;
    for (auto vecin : f[nod])
        dp[nod][0][0] += max(dp[vecin.first][0][0],dp[vecin.first][1][0]);
    vector<vector<int>> d(f[nod].size());
    for (int i = 0; i < f[nod].size(); i++)
        d[i].resize(2);
    for (int i = 0; i < f[nod].size(); i++)
    {
        int fiu = f[nod][i].first,cost = f[nod][i].second;
        if (i == 0)
        {
            d[i][0] = max(dp[fiu][0][0],dp[fiu][1][0]);
            d[i][1] = dp[fiu][0][0] + cost;
        }
        else
        {
            d[i][0] = d[i - 1][0] + max(dp[fiu][0][0],dp[fiu][1][0]);
            d[i][1] = max(d[i - 1][1] + max(dp[fiu][0][0],dp[fiu][1][0]),d[i - 1][0] + dp[fiu][0][0] + cost);
        }
    }
    dp[nod][1][0] = d[f[nod].size() - 1][1] + t[nod].second;

    d.clear();
    d.resize(f[nod].size());
    for (int i = 0; i < f[nod].size(); i++)
        d[i].resize(2);
    for (int i = 0; i < f[nod].size(); i++)
    {
        int fiu = f[nod][i].first,cost = f[nod][i].second;
        if (i == 0)
        {
            d[i][0] = max(dp[fiu][0][0],dp[fiu][1][0]);
            d[i][1] = max(dp[fiu][0][1],dp[fiu][1][1]);
        }
        else
        {
            d[i][0] = d[i - 1][0] + max(dp[fiu][0][0],dp[fiu][1][0]);
            d[i][1] = max(d[i - 1][1] + max(dp[fiu][0][0],dp[fiu][1][0]),d[i - 1][0] + max(dp[fiu][0][1],dp[fiu][1][1]));
        }
    }
    dp[nod][0][1] = d[f[nod].size() - 1][1];
    vector<vector<vector<int>>> dd(f[nod].size());
    for (int i = 0; i < f[nod].size(); i++)
    {
        dd[i].resize(3);
        for (int j = 0; j < dd[i].size(); j++)
            dd[i][j].resize(2);
    }
    for (int i = 0; i < f[nod].size(); i++)
        for (int j = 0; j < 3; j++)
            for (int q = 0; q < 2; q++)
                dd[i][j][q] = -inf;
    for (int i = 0; i < f[nod].size(); i++)
    {
        int fiu = f[nod][i].first,cost = f[nod][i].second;
        if (i == 0)
        {
            dd[i][0][0] = max(dp[fiu][0][0],dp[fiu][1][0]);
            dd[i][1][0] = cost + dp[fiu][0][0];
            dd[i][1][1] = cost + dp[fiu][0][1];
        }
        else
        {
            dd[i][0][0] = dd[i - 1][0][0] + max(dp[fiu][0][0],dp[fiu][1][0]);
            dd[i][1][0] = max(dd[i - 1][1][0] + max(dp[fiu][0][0],dp[fiu][1][0]),dd[i - 1][0][0] + cost + dp[fiu][0][0]);
            dd[i][1][1] = max(dd[i - 1][1][1] + max(dp[fiu][0][0],dp[fiu][1][0]),dd[i - 1][0][0] + cost + dp[fiu][0][1]);
            dd[i][2][0] = max(dd[i - 1][2][0] + max(dp[fiu][0][0],dp[fiu][1][0]),dd[i - 1][1][0] + cost + dp[fiu][0][0]);
            dd[i][2][1] = max(dd[i - 1][2][1] + max(dp[fiu][0][0],dp[fiu][1][0]),dd[i - 1][1][0] + cost + dp[fiu][0][1]);
            dd[i][2][1] = max(dd[i][2][1],dd[i - 1][1][1] + cost + dp[fiu][0][0]);
        }
    }
    dp[nod][0][1] = max(dp[nod][0][1],max(dd[f[nod].size() - 1][2][0],dd[f[nod].size() - 1][2][1]));

    d.clear();
    d.resize(f[nod].size());
    for (int i = 0; i < f[nod].size(); i++)
        d[i].resize(2),d[i][0] = d[i][1] = -inf;
    for (int i = 0; i < f[nod].size(); i++)
    {
        int fiu = f[nod][i].first,cost = f[nod][i].second;
        if (i == 0)
        {
            d[i][0] = max(dp[fiu][0][0],dp[fiu][1][0]);
            d[i][1] = dp[fiu][0][1] + cost;
        }
        else
        {
            d[i][0] = d[i - 1][0] + max(dp[fiu][0][0],dp[fiu][1][0]);
            d[i][1] = max(d[i - 1][1] + max(dp[fiu][0][0],dp[fiu][1][0]),d[i - 1][0] + dp[fiu][0][1] + cost);
        }
    }
    dp[nod][1][1] = d[f[nod].size() - 1][1] + t[nod].second;
    //cout << nod << ' ' << dp[nod][0][0] << ' ' << dp[nod][0][1] << ' ' << dp[nod][1][0] << ' ' << dp[nod][1][1] << endl;
}

signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    cin >> n;
    for (int i = 1; i < n; i++)
    {
        int x,y,z;
        cin >> x >> y >> z;
        g[x].push_back({y,z});
        g[y].push_back({x,z});
    }
    if (n == 2)
    {
        cout << 0;
        return 0;
    }
    dfs(1);
    solve(1);
    cout << max(dp[1][0][0],dp[1][0][1]);
    return 0;
}

Compilation message (stderr)

beads.cpp: In function 'void solve(long long int)':
beads.cpp:68:23: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   68 |     for (int i = 0; i < f[nod].size(); i++)
      |                     ~~^~~~~~~~~~~~~~~
beads.cpp:70:23: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   70 |     for (int i = 0; i < f[nod].size(); i++)
      |                     ~~^~~~~~~~~~~~~~~
beads.cpp:88:23: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   88 |     for (int i = 0; i < f[nod].size(); i++)
      |                     ~~^~~~~~~~~~~~~~~
beads.cpp:90:23: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   90 |     for (int i = 0; i < f[nod].size(); i++)
      |                     ~~^~~~~~~~~~~~~~~
beads.cpp:92:35: warning: unused variable 'cost' [-Wunused-variable]
   92 |         int fiu = f[nod][i].first,cost = f[nod][i].second;
      |                                   ^~~~
beads.cpp:106:23: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  106 |     for (int i = 0; i < f[nod].size(); i++)
      |                     ~~^~~~~~~~~~~~~~~
beads.cpp:109:27: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::vector<long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  109 |         for (int j = 0; j < dd[i].size(); j++)
      |                         ~~^~~~~~~~~~~~~~
beads.cpp:112:23: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  112 |     for (int i = 0; i < f[nod].size(); i++)
      |                     ~~^~~~~~~~~~~~~~~
beads.cpp:116:23: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  116 |     for (int i = 0; i < f[nod].size(); i++)
      |                     ~~^~~~~~~~~~~~~~~
beads.cpp:139:23: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  139 |     for (int i = 0; i < f[nod].size(); i++)
      |                     ~~^~~~~~~~~~~~~~~
beads.cpp:141:23: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  141 |     for (int i = 0; i < f[nod].size(); i++)
      |                     ~~^~~~~~~~~~~~~~~

• Subtask 1: 13 / 13
• Subtask 2: 15 / 15
• Subtask 3: 29 / 29
• Subtask 4: 43 / 43