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.
Note: A leaf is a node with no children.
Example:
Given binary tree [3,9,20,null,null,15,7],
3
/ \
9 20
/ \
15 7
return its depth = 3.
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
class Solution {
public boolean isBalanced(TreeNode root) {
if(root == null) return true;
int l = depth(root.left);
int r = depth(root.right);
return Math.abs(l - r) < 2 && isBalanced(root.left) && isBalanced(root.right);
}
public int depth(TreeNode root){
if(root == null) return 0;
return Math.max(depth(root.left), depth(root.right)) + 1;
}
}
在maxDepth of BST的基础上进一步做文章。