英文:
How do I randomly insert nodes into a binary search tree?
问题
public void Insert(Comparable key, Object data){// Create nodeNode node = new Node(key, data);// Walk down the treeNode parent = null;Node child = root;while (child != null){// Parent goes downparent = child;// Child goes downif (key.compareTo(child.GetKey()) == 0)throw new RuntimeException("Duplicate key.");else if (key.compareTo(child.GetKey()) < 0)child = child.left;elsechild = child.right;}// Hang new node from parent or make it the rootnode.parent = parent;if (parent == null)root = node;else if (key.compareTo(parent.GetKey()) < 0)parent.left = node;elseparent.right = node;}class Test{public static void main(String args[]){Tree tree = new Tree();// Create keysNode n1 = new Node(null, "1");Node n2 = new Node(null, "2");Node n3 = new Node(null, "3");Node n4 = new Node(null, "4");Node n5 = new Node(null, "5");Node n6 = new Node(null, "6");Node n7 = new Node(null, "7");// Create ScannerScanner scanner = new Scanner(System.in);System.out.print("Enter 'sorted' or 'random': ");String s = scanner.nextLine();if (s.equals("sorted")){tree.Insert("1", n1.GetData());tree.Insert("2", n2.GetData());tree.Insert("3", n3.GetData());tree.Insert("4", n4.GetData());tree.Insert("5", n5.GetData());tree.Insert("6", n6.GetData());tree.Insert("7", n7.GetData());}if (s.equals("random")){tree.Insert("5", n5.GetData());tree.Insert("2", n2.GetData());tree.Insert("1", n1.GetData());tree.Insert("3", n3.GetData());tree.Insert("6", n6.GetData());tree.Insert("7", n7.GetData());tree.Insert("4", n4.GetData());}if (!s.equals("random") && !s.equals("sorted"))throw new RuntimeException("Invalid input.");}}
英文:
I'm a student learning about data structures in Java. I'm less than a beginner so please don't criticize my code too hardly :).
I want to randomly insert nodes into a binary search tree, but don't know how to do this if not manually.
I'll paste the Insert() method here and how I was previously inserting. Also I'm getting a compilation error because of the scanner. Any idea why?
{// Create nodeNode node = new Node(key, data);// Walk down the treeNode parent = null;Node child = root;while (child != null){// Parent goes downparent = child;// Child goes downif (key.compareTo(child.GetKey()) == 0)throw new RuntimeException("Duplicate key.");else if (key.compareTo(child.GetKey()) < 0)child = child.left;elsechild = child.right;}// Hang new node from parent or make it the rootnode.parent = parent;if (parent == null)root = node;else if (key.compareTo(parent.GetKey()) < 0)parent.left = node;elseparent.right = node;}import java.util.Scanner;class Test{public static void main(String args[]){Tree tree = new Tree();// Create keysNode n1 = new Node(null, "1");Node n2 = new Node(null, "2");Node n3 = new Node(null, "3");Node n4 = new Node(null, "4");Node n5 = new Node(null, "5");Node n6 = new Node(null, "6");Node n7 = new Node(null, "7");// Create ScannerScanner scanner = new Scanner();System.out.print("Enter 'sorted' or 'random': ");String s = scanner.nextLine();if (s == "sorted")tree.Insert("1", n1.GetData());tree.Insert("2", n2.GetData());tree.Insert("3", n3.GetData());tree.Insert("4", n4.GetData());tree.Insert("5", n5.GetData());tree.Insert("6", n6.GetData());tree.Insert("7", n7.GetData());if (s == "random")tree.Insert("5", n5.GetData());tree.Insert("2", n2.GetData());tree.Insert("1", n1.GetData());tree.Insert("3", n3.GetData());tree.Insert("6", n6.GetData());tree.Insert("7", n7.GetData());tree.Insert("4", n4.GetData());if (s != "random" && s != "sorted")throw new RuntimeException("Invalid input.");}}</details># 答案1**得分**: 0以下是翻译好的内容：在`Collections`类中有一个标准库方法可以对列表进行随机排序。要使用它，我们必须创建一个包含数据的列表，然后调用`Collections.shuffle`方法：```javaList<String> data = new ArrayList();for (int i = 1; i <= 7; i++) {data.add(String.valueOf(i));}Collections.shuffle(data);
现在您可以将数据插入到树中：
for (String item: data) {tree.Insert(item, item);}
关于编译错误，没有一个不带参数的Scanner构造函数。您可能想要传入系统的标准输入流。
// 创建ScannerScanner scanner = new Scanner(System.in);
我还注意到另一件事：您不能使用==来比较字符串，比如if (s == "sorted")，您必须使用equals方法：if (s.equals("sorted"))。
还有一件事，您需要在if语句中使用大括号{ }。否则，您希望有条件地运行的内容将始终运行。
if (s.equals("sorted")) {tree.Insert("1", n1.GetData());tree.Insert("2", n2.GetData()); // <-- 无论s是什么都会运行}
英文:
There is a standard library method in the Collections class to shuffle a list. To use it, we must create a List with the data, and then call Collections.shuffle:
List<String> data = new ArrayList();for (int i = 1; i <= 7; i++) {data.add(String.valueOf(i));}Collections.shuffle(data);
Now you can just insert the data into the tree:
for (String item: data) {tree.Insert(item, item);}
Regarding the compilation error, there is no Scanner constructor that takes no arguments. You probably wanted to pass in the system standard input stream.
// Create ScannerScanner scanner = new Scanner(System.in);
Another thing I noticed: you can't compare strings with == like in if (s == "sorted") you must use the equals method instead: if (s.equals("sorted"))
Yet another thing, you need to use brackets { } with if-statements. Otherwise things that you meant to run conditionally will run always.
if (s == "sorted")tree.Insert("1", n1.GetData());tree.Insert("2", n2.GetData()); // <-- runs no matter what s is
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