【剑指offer】二叉树的中序遍历

描述：

给出一棵二叉树,返回其中序遍历

样例：

给出二叉树 {1,#,2,3},

   1
    \
     2
    /
   3

返回 [1,3,2].

Java代码：

/**
 * Definition of TreeNode:
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left, right;
 *     public TreeNode(int val) {
 *         this.val = val;
 *         this.left = this.right = null;
 *     }
 * }
 */
public class Solution {
    /**
     * @param root: The root of binary tree.
     * @return: Inorder in ArrayList which contains node values.
     */
    public ArrayList<Integer> inorderTraversal(TreeNode root) {
        ArrayList<Integer> list= new ArrayList<Integer>();
        
        traversal(list,root);
        
        return list;
    }
	
	public void traversal(ArrayList<Integer> list,TreeNode root){
		if(root == null){
			return;
		}
		
		traversal(list,root.left);
		list.add(root.val);
		traversal(list,root.right);
	}
}