Complete the function in the editor below, which has parameter: a pointer to the root of a binary tree. It must print the values in the tree's preorder traversal as a single line of space-separated values.
Our test code passes the root node of a binary tree to the preOrder function.
Nodes in the tree
Print the tree's preorder traversal as a single line of space-separated values.
1 2 5 3 4 6
The preorder traversal of the binary tree is printed.