Submission #386247

#	Time	Username	Problem	Language	Result	Execution time	Memory
386247		Drew_	Beads and wires (APIO14_beads)	C++14	0 / 100	5 ms	5120 KiB

beads

#include <iostream>
#include <vector>
#include <algorithm>
#include <assert.h>
using namespace std;

#define pb push_back
#define ii pair<int, int>
#define f1 first
#define s2 second

const int MAX = 2e5 + 7;

//dp[x][0]: do not use the edge to the parent of node x
//dp[x][1]: used the edge to the parent of node x

bool vst[MAX];

int dp[MAX][2];
vector<ii> adj[MAX];

void dfs(int node, int par, int par_val)
{
	vector<int> v0;
	vector<int> v1;
	vector<int> edge;

	vst[node] = true;

	for (ii to : adj[node])
	{
		if (to.f1 != par)
		{
			if (vst[to.f1])
				assert(0);

			dfs(to.f1, node, to.s2);
			v0.pb(dp[to.f1][0]);
			v1.pb(dp[to.f1][1]);
			edge.pb(to.s2);
		}
	}

	//not using node as center
	for (int i = 0; i < v0.size(); ++i)
		dp[node][0] += max(v0[i], v1[i]);

	//using two edges
	vector<int> val;
	for (int i = 0; i < v0.size(); ++i)
	{
		if (v0[i] >= v1[i]) val.pb(edge[i]);
		else val.pb(edge[i] + v0[i] - v1[i]);
	}
	sort(val.begin(), val.end(), greater<int>());

	if (val.size() >= 1)
		dp[node][1] = dp[node][0] + val[0] + par_val;
	if (val.size() >= 2)
		dp[node][0] = max(dp[node][0], dp[node][0] + val[0] + val[1]);
}

int main()
{
	ios :: sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);

	int n;
	cin >> n;

	for (int i = 0; i < n-1; ++i)
	{
		int u, v, w;
		cin >> u >> v >> w;

		adj[u].pb({v, w});
		adj[v].pb({u, w});
	}

	dfs(1, -1, -1);
	cout << dp[1][0] << '\n';

	return 0;
}

Compilation message (stderr)

beads.cpp: In function 'void dfs(int, int, int)':
beads.cpp:45:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   45 |  for (int i = 0; i < v0.size(); ++i)
      |                  ~~^~~~~~~~~~~
beads.cpp:50:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   50 |  for (int i = 0; i < v0.size(); ++i)
      |                  ~~^~~~~~~~~~~

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