1. 题目
2. 思路
(1) BFS
- 利用队列实现层序遍历，返回层数即可。
(2) DFS
- 利用递归实现前序遍历，返回最大深度即可。
3. 代码
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;
public class Test {
public static void main(String[] args) {
}
}
class Node {
public int val;
public List<Node> children;
public Node() {
}
public Node(int _val) {
val = _val;
}
public Node(int _val, List<Node> _children) {
val = _val;
children = _children;
}
};
class Solution {
public int maxDepth(Node root) {
if (root == null) {
return 0;
}
int res = 0;
Queue<Node> queue = new LinkedList<>();
queue.offer(root);
while (!queue.isEmpty()) {
res++;
for (int i = queue.size(); i > 0; i--) {
Node node = queue.poll();
for (Node child : node.children) {
queue.offer(child);
}
}
}
return res;
}
}
class Solution1 {
private int res;
private int cur;
public int maxDepth(Node root) {
if (root == null) {
return 0;
}
dfs(root);
return res;
}
private void dfs(Node root) {
if (root == null) {
return;
}
cur++;
res = Math.max(res, cur);
for (Node child : root.children) {
dfs(child);
}
cur--;
}
}