Tree InOrder Traversal

Implement an InOrder traversal of a binary tree. In this traversal, the left subtree is visited first, then the root node, and finally the right subtree.

The definition of the tree node is as follows:

// Java
class TreeNode
{
public:
  int val;
  TreeNode left;
  TreeNode right;
  TreeNode(int x) {
    val = x;
    left = NULL;
    right = NULL;
  }
};

// C++
class TreeNode
{
public:
  int val;
  TreeNode *left;
  TreeNode *right;
  TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};

Implement the function InOrder that prints all the vertices of the tree in one line in the order of an InOrder traversal. Separate the values with a single space.

// Java
void InOrder(TreeNode tree)

// C++
void InOrder(TreeNode *tree)

Examples

During the InOrder traversal, the vertices will be printed in the following order: 1 2 3 4 9 10 16.