Maximum Depth of Binary Tree Problem

Problem Description
level: easy
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.
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Example

Given a binary tree as follow:

/ \

2 3

/ \

4 5

The maximum depth is 3.

Solution:
consider use divide and conquer approach


    /**
     * @param root: The root of binary tree.
     * @return: An integer.
     */
    public int maxDepth(TreeNode root) {
    	if(root == null) return 0;
    	
    	// divide
    	int left = maxDepth(root.left);
    	int right = maxDepth(root.right);
    	// conquer
    	return Math.max(right, left) + 1;
    }