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DiameterOfTree.java
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DiameterOfTree.java
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import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.LinkedList;
import java.util.List;
import java.util.StringTokenizer;
public class DiameterOfTree {
private static Node[] resultArr;
private static boolean[] visitArr;
private static int maxWeight = Integer.MIN_VALUE;
private static int maxIndex = 1;
public static void main(String[] args) throws Exception {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
StringTokenizer st;
int N = Integer.parseInt(br.readLine());
initResultArr(N);
initVisitArr(N);
for(int i = 0; i < N-1; i++) {
st = new StringTokenizer(br.readLine(), " ");
int from = Integer.parseInt(st.nextToken());
int to = Integer.parseInt(st.nextToken());
int weight = Integer.parseInt(st.nextToken());
resultArr[from].getLink().add(new Link(to, weight));
resultArr[to].getLink().add(new Link(from, weight));
}
visitArr[1] = true;
dfs(1, 0);
initVisitArr(N);
maxWeight = Integer.MIN_VALUE;
visitArr[maxIndex] = true;
dfs(maxIndex, 0);
printResult();
}
private static void initResultArr(int length) {
resultArr = new Node[length + 1];
for(int i = 1; i < resultArr.length; i++) {
resultArr[i] = new Node(i);
}
}
private static void initVisitArr(int length) {
visitArr = new boolean[length + 1];
}
private static int dfs(int index, int weight) {
for(Link link : resultArr[index].getLink()) {
int to = link.getDestination();
int cost = link.getWeight();
if(visitArr[to]) continue;
visitArr[to] = true;
int weightValue = dfs(to, weight + cost);
if(weightValue >= maxWeight) {
maxWeight = weightValue;
maxIndex = to;
}
}
return weight;
}
private static void printResult() {
if(resultArr.length == 2) {
System.out.println(0);
return;
}
System.out.println(maxWeight);
}
private static class Node {
private int number;
private List<Link> link = new LinkedList<>();
public Node(int number) {
this.number = number;
}
public int getNumber() {
return this.number;
}
public List<Link> getLink() {
return this.link;
}
}
private static class Link {
private int destination;
private int weight;
public Link(int destination, int weight) {
this.destination = destination;
this.weight = weight;
}
public int getDestination() {
return this.destination;
}
public int getWeight() {
return this.weight;
}
}
}