Submission #1011870

#	Time	Username	Problem	Language	Result	Execution time	Memory
1011870		andrei_iorgulescu	Beads and wires (APIO14_beads)	C++14	0 / 100	5 ms	9820 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];

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);
        }
    }
}

void calc_dp0(int nod)
{
    vector<vector<int>> d(f[nod].size());
    for (int i = 0; i < f[nod].size(); i++)
        d[i].resize(3);
    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][2] = -inf;
            d[i][0] = max(dp[fiu][0],dp[fiu][1]);
            d[i][1] = dp[fiu][0] + cost;
        }
        else
        {
            d[i][0] = d[i - 1][0] + max(dp[fiu][0],dp[fiu][1]);
            d[i][1] = max(d[i - 1][0] + dp[fiu][0] + cost,d[i - 1][1] + max(dp[fiu][0],dp[fiu][1]));
            d[i][2] = max(d[i - 1][1] + dp[fiu][0] + cost,d[i - 1][2] + max(dp[fiu][0],dp[fiu][1]));
        }
    }
    dp[nod][0] = max(d[f[nod].size() - 1][0],d[f[nod].size() - 1][2]);
}

void calc_dp1(int nod)
{
    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],dp[fiu][1]);
            d[i][1] = dp[fiu][0] + cost;
        }
        else
        {
            d[i][0] = d[i - 1][0] + max(dp[fiu][0],dp[fiu][1]);
            d[i][1] = max(d[i - 1][0] + dp[fiu][0] + cost,d[i - 1][1] + max(dp[fiu][0],dp[fiu][1]));
        }
    }
    dp[nod][1] = d[f[nod].size() - 1][1] + t[nod].second;
}

/*
8
1 2 1
1 3 2
1 4 3
1 5 10
5 6 1
5 7 2
5 8 4
*/

void solve(int nod)
{
    for (auto vecin : f[nod])
        solve(vecin.first);
    if (f[nod].size() == 0)
    {
        dp[nod][0] = 0;
        dp[nod][1] = -inf;
        return;
    }
    calc_dp0(nod);
    if (nod != root)
        calc_dp1(nod);
}

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;
    }
    for (int i = 1; i <= n; i++)
        if (g[i].size() != 1)
            root = i;
    dfs(root);
    solve(root);
    cout << dp[root][0];
    return 0;
}

Compilation message (stderr)

beads.cpp: In function 'void calc_dp0(long long int)':
beads.cpp:31:23: 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]
   31 |     for (int i = 0; i < f[nod].size(); i++)
      |                     ~~^~~~~~~~~~~~~~~
beads.cpp:33:23: 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]
   33 |     for (int i = 0; i < f[nod].size(); i++)
      |                     ~~^~~~~~~~~~~~~~~
beads.cpp: In function 'void calc_dp1(long long int)':
beads.cpp:55:23: 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]
   55 |     for (int i = 0; i < f[nod].size(); i++)
      |                     ~~^~~~~~~~~~~~~~~
beads.cpp:57:23: 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]
   57 |     for (int i = 0; i < f[nod].size(); i++)
      |                     ~~^~~~~~~~~~~~~~~

• Subtask 1: 0 / 13
• Subtask 2: 0 / 15
• Subtask 3: 0 / 29
• Subtask 4: 0 / 43