[英]Recursive Preorder traversal running untill stack overflows, (BST) in JAVA
我正在用insert和preorder方法在Java中實現簡單的Binary Search Tree。 我正在遇到無限的預執行,直到stackoverflows。
這是Node類:
public class Node {
private Node right, left;
private int data;
public Node(Node right, Node left, int data) {
super();
this.right = right;
this.left = left;
this.data = data;
}
public Node() {
super();
this.right = this.left = null;
this.data = 0;
}
public Node getRight() {
return right;
}
public void setRight(Node n) {
this.right = n;
}
public Node getLeft() {
return left;
}
public void setLeft(Node n) {
this.left = n;
}
public int getData() {
return data;
}
public void setData(int data) {
this.data = data;
}
}
這是BinarySearchTree類:
public class BinarySearchTree {
private Node root;
public BinarySearchTree() {
root = null;
}
public Node insert(int data) {
root = insertInto(root, data);
return root;
}
private Node insertInto(Node node, int data) {
if (node == null) {
Node temp = new Node();
temp.setData(data);
return temp;
} else if (data < node.getData()) {
node.setLeft(insertInto(node.getLeft(), data));
} else if (data > node.getData()) {
node.setRight(insertInto(node.getRight(), data));
}
return root;
}
public void preorder() {
getPreorder(root);
}
private void getPreorder(Node root) {
if (root == null)
return;
System.out.println(root);
getPreorder(root.getLeft());
getPreorder(root.getRight());
}
}
這是主要的課程:
public class BstMain {
public static void main(String args[])
{
BinarySearchTree bst = new BinarySearchTree();
bst.insert(10);
bst.insert(9);
bst.insert(15);
bst.insert(8);
bst.insert(20);
bst.preorder();
}
}
這是輸出:
Node [data=10]
Node [data=10]
Node [data=10]
Node [data=10]
Node [data=10]
Node [data=10]
Node [data=10]
Node [data=10]
Exception in thread "main" java.lang.StackOverflowError
at sun.nio.cs.SingleByte.withResult(Unknown Source)
at sun.nio.cs.SingleByte.access$000(Unknown Source)
at sun.nio.cs.SingleByte$Encoder.encodeArrayLoop(Unknown Source)
at sun.nio.cs.SingleByte$Encoder.encodeLoop(Unknown Source)
at java.nio.charset.CharsetEncoder.encode(Unknown Source)
at sun.nio.cs.StreamEncoder.implWrite(Unknown Source)
at sun.nio.cs.StreamEncoder.write(Unknown Source)
at java.io.OutputStreamWriter.write(Unknown Source)
at java.io.BufferedWriter.flushBuffer(Unknown Source)
at java.io.PrintStream.write(Unknown Source)
at java.io.PrintStream.print(Unknown Source)
at java.io.PrintStream.println(Unknown Source)
at bsTree.BinarySearchTree.getPreorder(BinarySearchTree.java:42)
at bsTree.BinarySearchTree.getPreorder(BinarySearchTree.java:43)
at bsTree.BinarySearchTree.getPreorder(BinarySearchTree.java:43)
at bsTree.BinarySearchTree.getPreorder(BinarySearchTree.java:43)
我認為插入邏輯有問題,無法弄清楚這是什么。
問題出在insertInto(...)
:
} else if (data < node.getData()) {
node.setLeft(insertInto(node.getLeft(), data));
} else if (data > node.getData()) {
node.setRight(insertInto(node.getRight(), data));
}
return root;
在這兩種情況中的任何一種情況下,最終都將左/右子級設置為根節點,因此要創建一個循環。 這就是導致無限遞歸的原因。
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