Chapter 17, Problem 19E

Program Plan Intro

A method “evenLevels()”

Program plan:

• Define the method “evenLevels()”,
  • Assign the value returned from the parameterized method “evenLevels()”.
  • Return the list.
• Define the parameterized method “evenLevels()”,
  • Check whether the root of the binary tree is not null,
    • If it is true, assign the value returned from the method “evenLevels()” to the left child of the node.
    • Assign the value returned from the method “evenLevels()” to the right child of the node.
    • Check whether the right and left child of the node is null and the remainder when dividing height of the tree by “2” is “1”,
      • `If it is true, assign the node with null value.
        • Return the node.