leetcode-104 Maximum Depth of Binary Tree

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.

 

找出最大深度：  

    public int maxDepth(TreeNode root) {         return maxDepth( root, 0, 0);     }          public int maxDepth(TreeNode root,int value,int res) {         if(root == null) return res >= value? res:value;         else{             return Math.max(maxDepth(root.left,value+1,res),maxDepth(root.right,value+1,res));         }     }