rose.cpp

#include <cstdlib>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <climits>
#include <iostream>
 
using namespace std;
 
struct Node{
	Node(){visited=false;}
	bool visited;
	vector<int> edges;
	vector<int> egeval;
};
 
int n,cn;
vector<Node> nodes;
 
int solve(int n, int eval){
	//cout << n << " " << eval << endl;
	nodes[n].visited = true;
	int alt = 0;
	int cc  = 0;
	for( int i = 0; i < nodes[n].edges.size(); i++ ){
		if(!nodes[nodes[n].edges[i]].visited){
		alt+=solve(nodes[n].edges[i],nodes[n].egeval[i]);
		cc++;}
	}
	if(!cc)return eval;
	//cout << "alt " << alt << endl; 
	return min(eval,alt);
}
 
int main(int argc, char * argv[]){
	int a,b,c;
	while(scanf("%d %d",&n,&cn)==2){
		nodes.resize(0);
		nodes.resize(n);
		cn--;
		for( int i = 0; i < (n-1); i++ ){
			scanf("%d%d%d",&a,&b,&c);
			a--;b--;
			nodes[a].edges.push_back(b);
			nodes[b].edges.push_back(a);
			nodes[a].egeval.push_back(c);
			nodes[b].egeval.push_back(c);
		}
		printf("%d\n",solve(cn,INT_MAX));
	}
	return 0;
}