Sum of Left Leaves

Given an array of integers. Create a Binary Search Tree from these numbers. If the inserted value equals the current node, insert it into the right subtree.

Implement the method SumLeft, which returns the sum of all left leaves in the tree.

Write the code according to the following interface:

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

class Tree
{
public:
  TreeNode *head;
  Tree() : head(NULL) {};
  void Insert(int val); // Insert value val into the Binary Search Tree
  int SumLeft(void); // Return the sum of all left leaves in the tree
};

You can create (use) additional methods if necessary.