題目描述
Given a binary tree, find its maximum depth.
The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.
Java代碼實現(xiàn)1 - 遞歸
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public int maxDepth(TreeNode root) {
return root == null ? 0 : Math.max(maxDepth(root.left), maxDepth(root.right)) + 1;
}
}
Java代碼實現(xiàn)2 - BFS
public class Solution {
public int maxDepth(TreeNode root) {
if (root == null) {
return 0;
}
Queue<TreeNode> queue = new LinkedList<>();
queue.offer(root);
int count = 0;
while (!queue.isEmpty()) {
int remainingLevelSize = queue.size();
while (remainingLevelSize-- > 0) {
TreeNode curNode = queue.poll();
nodeEnqueue(curNode.left, queue);
nodeEnqueue(curNode.right, queue);
}
count ++;
}
return count;
}
private void nodeEnqueue(TreeNode curNode, Queue<TreeNode> queue) {
if (curNode != null) {
queue.offer(curNode);
}
}
}
