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removeLeaves

Language/Type: C++ binary trees pointers recursion

Write a function named removeLeaves that accepts a reference to a pointer to the root of a binary tree of integers. Your function should remove the leaf nodes from a tree. A leaf is a node that has empty (nullptr) left and right subtrees. If your function is called on an empty tree, it does not change the tree because there are no nodes of any kind (leaf or not). Free the memory for any removed nodes.

Constraints: You must implement your function recursively and without using loops. Do not construct any new BinaryTreeNode objects in solving this problem (though you may create as many BinaryTreeNode* pointer variables as you like). Do not use any auxiliary data structures to solve this problem (no array, vector, stack, queue, string, etc).

Assume that you are using the BinaryTreeNode structure as defined below: 

struct BinaryTreeNode {
    int data;
    BinaryTreeNode* left;
    BinaryTreeNode* right;
};
Function: Write a C++ function as described, not a complete program.

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