104 Maximum Depth of Binary Tree
Question:
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.
Lesson Learned:
// 似乎用boolean的题可以用 return xxx && yyy来做, int的题可以用 return xxx + yyy来做
第二次的update,我用了只扫描path的方法,因为数level这种还是直接用path的template省的用脑子想了。
Code:
/**
* 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 helper(root);
}
private int helper(TreeNode root) {
if (root == null) {
return 0;
}
// 似乎用boolean的题可以用 return xxx && yyy来做, int的题可以用 return xxx + yyy来做
return 1 + Math.max(maxDepth(root.left), maxDepth(root.right));
}
}
updated (12.19.15)
/**
* 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 helper(root);
}
private int helper(TreeNode root) {
if (root == null) {
return 0;
}
if (root.left == null) {
return 1 + helper(root.right);
}
if (root.right == null) {
return 1 + helper(root.left);
}
return 1 + Math.max(helper(root.left), helper(root.right));
}
}