Chapter 17, Problem 1E

Program Plan Intro

A method “countLeftNodes()”

Program plan:

• Define the method “countLeftNodes()”,
  • Return the value returned from the parameterized method “countLeftNodes()”.
• Define the parameterized method “countLeftNodes()”,
  • Check whether the root of the tree is null,
    • If it is true, return “0”.
      • Otherwise, check whether the left node of the tree is null,
        • Return the value returned from the parameterized method “countLeftNodes()”.
      • Otherwise, return the calculated value.

Program Description Answer

This program demonstrates the method “countLeftNodes()” that return the number of left children in the tree.

Explanation of Solution

Code:

//Define the method

public int countLeftNodes()

{

/*Return the value returned from the parameterized method "countLeftNodes()"*/

    return countLeftNodes(overallRoot);

}

//Define the parameterized method method "countLeftNodes()"

private int countLeftNodes(IntTreeNode root1)

{

    //Check whether the root is null

    if (root1 == null)

    {

        //Return "0"

        return 0;

    }

/*Otherwise, check whether the left node of the tree is null*/

    else if (root1.left == null)

    {

/*Return the value returned from the parameterized method "countLeftNodes()"*/

        return countLeftNodes(root1.right);

    }

    else

    {

        //Return the calculated value

return 1 + countLeftNodes(root1.left) + countLeftNodes(root1.right);

    }

}