Main.java

 
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.StringTokenizer;
 
public class Main {
 
    protected int nodesCnt;
    protected int centralNode;
    protected int[][] edges;
    protected int[][] edgesPrice;
    protected int[] edgesCnt;
 
    public static void main(String[] args) throws Exception {
        Main p = new Main();
        p.run();
    }
 
    protected void run() throws Exception {
        while (input.ready()) {
            this.nodesCnt = this.nextInt();
            this.centralNode = this.nextInt();
 
            edges = new int[nodesCnt + 1][nodesCnt];
            edgesPrice = new int[nodesCnt + 1][nodesCnt];
            edgesCnt = new int[nodesCnt + 1];
 
            for (int i = 0; i < this.nodesCnt - 1; i++) {
                int b = this.nextInt();
                int e = this.nextInt();
                int price = this.nextInt();
                edges[b][edgesCnt[b]] = e;
                edges[e][edgesCnt[e]] = b;
                edgesPrice[b][edgesCnt[b]] = price;
                edgesPrice[e][edgesCnt[e]] = price;
                edgesCnt[b]++;
                edgesCnt[e]++;
            }
            System.out.println(getPrice(centralNode, -10));
        }
    }
 
    protected int getPrice(int node, int parent) {
        int closeMePrice = 0;
        int closeChildrenPrice = 0;
        for (int i = 0; i < edgesCnt[node]; i++) {
            if (edges[node][i] != parent) {
                closeMePrice += edgesPrice[node][i];
                closeChildrenPrice += getPrice(edges[node][i], node);
            }
        }
        if (closeChildrenPrice == 0) {
            return closeMePrice;
        }
        return Math.min(closeMePrice, closeChildrenPrice);
    }
 
    StringTokenizer st = new StringTokenizer("");
    BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
 
    public String nextToken() throws Exception {
        while (!st.hasMoreTokens()) {
            st = new StringTokenizer(input.readLine());
        }
        return st.nextToken();
    }
 
    public int nextInt() throws Exception {
        return Integer.parseInt(nextToken());
    }
 
    public String nextLine() throws Exception {
        return input.readLine();
    }
 
}