How to find the depth of a binary tree

Depth of a binary tree:
Depth of a binary tree is the maximum length of all paths. Nodes from the root to a leaf form a path.

For example, the depth of the binary tree in the below figure is 4, with the longest path through nodes 1, 2, 5, and 7.

A binary Tree with depth 4

Solution: Depth of a binary tree is the length of the longest path.

If a binary tree has only one node, its depth is 1. If the root node of a binary tree has only a left sub-tree, its depth is the depth of the left sub-tree plus 1(root node). Similarly, its depth is the depth of the right sub-tree plus 1(root node) if the root node has only a right sub-tree. What if the root node has both left sub-tree and right sub-tree? It is the greater/max value of the depth of the left and right sub-trees plus 1(root node).

 For example, the root node of the binary tree in the above figure has both left and right sub-trees. The depth of the left sub-tree rooted at node 2 is 3, and the depth of the right sub-tree rooted at node 3 is 2, so the depth of the whole binary tree is 4; 1 plus the greater value of 3 and 2.

 It is easy to implement this solution recursively, with little modification on the post-order traversal
algorithm, as shown below:

int TreeDepth(Binarytree Node* pRoot)

{

   int nLeft, nRight;

   if(root == NULL)

        return 0;

    nLeft = TreeDepth(pRoot->pLeft);

    nRight = TreeDepth(pRoot->pRight);

    return (nLeft > nRight) ? (nLeft + 1) : (nRight + 1);

}