java - 删除二叉树中的所有叶子

Question

此方法应该从二叉树(没有左右分支)中删除所有叶子，但由于某种原因，它只从二叉树中删除叶子的一个实例。这是为什么？我认为基本情况负责通过将parent.left或parent.right设置为null来切断与父节点的联系。如果它不是叶子，它将递归调用，直到遇到叶子。

这是我到目前为止所拥有的:

 private IntTreeNode overallRoot; // Beginning of the chain of nodes


    // post: Removes All leaves from a tree
     public void removeLeaves() {
     if (overallRoot == null) { // If empty tree
         return;
     } else {
         removeLeaves(overallRoot);
     }

 }

 // helper for removeLeaves
 private void removeLeaves(IntTreeNode root) {       
     if (root.left != null) { // tests left root
         if (root.left.left == null && root.left.right == null) { // if next left node is leaf (base case)
             root.left = null; // delete
         } else if (root.left.left != null && root.left.right == null) { // If next right is empty
             removeLeaves(root.left.left); // only check second left
         } else if (root.left.right != null && root.left.left == null) { // If next left is empty
             removeLeaves(root.left.right); 
         } else if (root.left.left != null && root.left.right != null) { // If next left/right isn't empty
             removeLeaves(root.left.left);
             removeLeaves(root.left.right);
         }
     }

     if (root.right != null) {
         if (root.right.left == null && root.right.right == null) { // if next left node is leaf (base case)
             root.right = null; // delete
         } else if (root.right.left != null && root.right.right == null) { // If next right is empty
             removeLeaves(root.right.left); // only check second left
         } else if (root.right.right != null && root.right.left == null) { // If next left is empty
             removeLeaves(root.right.right); 
         } else if (root.right.left != null && root.right.right != null) { // If next left/right isn't empty
             removeLeaves(root.right.left);
             removeLeaves(root.right.right);
         }
     }
 }

这是单个节点类:

public class IntTreeNode {
     public int data;
     public IntTreeNode left;
     public IntTreeNode right;

     // constructs a leaf node with given data
     public IntTreeNode(int data) {
         this(data, null, null);
     }

     // constructs a branch node with given data, left subtree,
     // right subtree
     public IntTreeNode(int data, IntTreeNode left, IntTreeNode right) {
         this.data = data;
         this.left = left;
         this.right = right;
     }
}

Answer 1

以自下而上的方式对树木进行结构修改通常会更清晰:

public IntTreeNode removeLeaves(IntTreeNode root) {
    if (root == null || root.isLeaf()) {
        return null;
    }
    root.left = removeLeaves(root.left);
    root.right = removeLeaves(root.right);
    return root;
}