|  |  |  | @ -194,3 +194,45 @@ class Solution { | 
			
		
	
		
			
				
					|  |  |  |  | } | 
			
		
	
		
			
				
					|  |  |  |  | ``` | 
			
		
	
		
			
				
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					|  |  |  |  | #### [55 - I. 二叉树的深度](https://leetcode-cn.com/problems/er-cha-shu-de-shen-du-lcof/) | 
			
		
	
		
			
				
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					|  |  |  |  | ```java | 
			
		
	
		
			
				
					|  |  |  |  | class Solution { | 
			
		
	
		
			
				
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					|  |  |  |  |     public int maxDepth(TreeNode root) { | 
			
		
	
		
			
				
					|  |  |  |  |         if (root == null) { | 
			
		
	
		
			
				
					|  |  |  |  |             return 0; | 
			
		
	
		
			
				
					|  |  |  |  |         } | 
			
		
	
		
			
				
					|  |  |  |  |         return Math.max(maxDepth(root.left), maxDepth(root.right)) + 1; | 
			
		
	
		
			
				
					|  |  |  |  |     } | 
			
		
	
		
			
				
					|  |  |  |  | } | 
			
		
	
		
			
				
					|  |  |  |  | ``` | 
			
		
	
		
			
				
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					|  |  |  |  | ```java | 
			
		
	
		
			
				
					|  |  |  |  | class Solution { | 
			
		
	
		
			
				
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					|  |  |  |  |     public int maxDepth(TreeNode root) { | 
			
		
	
		
			
				
					|  |  |  |  |         if (root == null) { | 
			
		
	
		
			
				
					|  |  |  |  |             return 0; | 
			
		
	
		
			
				
					|  |  |  |  |         } | 
			
		
	
		
			
				
					|  |  |  |  |         int result = 0; | 
			
		
	
		
			
				
					|  |  |  |  |         Deque<TreeNode> queue = new LinkedList<>(); | 
			
		
	
		
			
				
					|  |  |  |  |         queue.add(root); | 
			
		
	
		
			
				
					|  |  |  |  |         while (!queue.isEmpty()) { | 
			
		
	
		
			
				
					|  |  |  |  |             result++; | 
			
		
	
		
			
				
					|  |  |  |  |             int n = queue.size(); | 
			
		
	
		
			
				
					|  |  |  |  |             for (int i = 0; i < n; i++) { | 
			
		
	
		
			
				
					|  |  |  |  |                 TreeNode node = queue.poll(); | 
			
		
	
		
			
				
					|  |  |  |  |                 if (node.left != null) { | 
			
		
	
		
			
				
					|  |  |  |  |                     queue.add(node.left); | 
			
		
	
		
			
				
					|  |  |  |  |                 } | 
			
		
	
		
			
				
					|  |  |  |  |                 if (node.right != null) { | 
			
		
	
		
			
				
					|  |  |  |  |                     queue.add(node.right); | 
			
		
	
		
			
				
					|  |  |  |  |                 } | 
			
		
	
		
			
				
					|  |  |  |  |             } | 
			
		
	
		
			
				
					|  |  |  |  |         } | 
			
		
	
		
			
				
					|  |  |  |  |         return result; | 
			
		
	
		
			
				
					|  |  |  |  |     } | 
			
		
	
		
			
				
					|  |  |  |  | } | 
			
		
	
		
			
				
					|  |  |  |  | ``` | 
			
		
	
		
			
				
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