$//$ Initializes an iterator to the beginning of a tree $($i$.$e$.,$ first in$-$order node$)$

void tree$\_$iterator$\_$begin$($tree$\_$iterator$\_$t$*$ iter, tree$\_$node$\_$t$*$ root$)$

$\{$

$//$ IMPLEMENT THIS

$\}$

$//$ Updates an iterator to move to the next in$-$order node in the tree if possible

$//$ Moving past the last in$-$order node in the tree results in the iterator reaching a NULL state representing the end of the tree

void tree$\_$iterator$\_$next$($tree$\_$iterator$\_$t$*$ iter$)$

$\{$

$//$ IMPLEMENT THIS

$\}$ Given structs: typedef struct tree$\_$node $\{$

shape$\_$t$*$ shape; $//$ Shape associated with the node

struct tree$\_$node$*$ left; $//$ Left subtree

struct tree$\_$node$*$ right; $//$ Right subtree

$\}$ tree$\_$node$\_$t;

#define MAX$\_$DEPTH $30$

typedef struct $\{$

tree$\_$node$\_$t$*$ curr; $//$ Pointer to the current node

unsigned int depth; $//$ Current depth in the tree $($root is at depth $0)$

tree$\_$node$\_$t$*$ parents$[$MAX$\_$DEPTH$]$; $//$ Pointer to parent nodes

$\}$ tree$\_$iterator$\_$t; $//$ Helper struct for iterating through a tree $--$ represents a current location within the tree