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countLeftNodes

Language/Type: C++ binary trees pointers recursion
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Author: Marty Stepp (on 2016/08/27)

Write a function named countLeftNodes that accepts a pointer to the root of a binary tree of integers. Your function should return the number of left children in the tree. A left child is a node that appears as the root of the left-hand subtree of another node. For example, if a pointer named root points to the root of the tree below, the call of countLeftNodes(root) should return 4 because the tree has 4 left children (the nodes storing the values 5, 1, 4, and 7):

(3 (5 (1)) (2 (4 (7)) (6)))

Constraints: 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). Your function should not modify the tree's state; the state of the tree should remain constant with respect to your function.

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

struct BinaryTreeNode {
    int data;
    BinaryTreeNode* left;
    BinaryTreeNode* right;
    ...
}
Type your solution here:


This is a function problem. Write a C++ function as described. Do not write a complete program; just the function(s) above.

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