1.何为二叉搜索树
1.1二叉搜索树的接口设计
1.2添加节点
1.3元素比较方案
1.4相关代码
1.BinarySearchTree类
package com.mj;
import java.util.Comparator;
import java.util.LinkedList;
import java.util.Queue;
import com.mj.printer.BinaryTreeInfo;
@SuppressWarnings("unchecked")
public class BinarySearchTree<E> implements BinaryTreeInfo {
private int size;
private Node<E> root;
private Comparator<E> comparator;
public BinarySearchTree() {
this(null);
}
public BinarySearchTree(Comparator<E> comparator) {
this.comparator = comparator;
}
public int size() {
return size;
}
public boolean isEmpty() {
return size == 0;
}
public void clear() {
root = null;
size = 0;
}
public void add(E element) {
elementNotNullCheck(element);
// 添加第一个节点
if (root == null) {
root = new Node<>(element, null);
size++;
return;
}
// 添加的不是第一个节点
// 找到父节点
Node<E> parent = root;
Node<E> node = root;
int cmp = 0;
do {
cmp = compare(element, node.element);
parent = node;
if (cmp > 0) {
node = node.right;
} else if (cmp < 0) {
node = node.left;
} else { // 相等
node.element = element;
return;
}
} while (node != null);
// 看看插入到父节点的哪个位置
Node<E> newNode = new Node<>(element, parent);
if (cmp > 0) {
parent.right = newNode;
} else {
parent.left = newNode;
}
size++;
}
public void remove(E element) {
remove(node(element));
}
public boolean contains(E element) {
return node(element) != null;
}
private void remove(Node<E> node) {
if (node == null) return;
size--;
if (node.hasTwoChildren()) { // 度为2的节点
// 找到后继节点
Node<E> s = successor(node);
// 用后继节点的值覆盖度为2的节点的值
node.element = s.element;
// 删除后继节点
node = s;
}
// 删除node节点（node的度必然是1或者0）
Node<E> replacement = node.left != null ? node.left : node.right;
if (replacement != null) { // node是度为1的节点
// 更改parent
replacement.parent = node.parent;
// 更改parent的left、right的指向
if (node.parent == null) { // node是度为1的节点并且是根节点
root = replacement;
} else if (node == node.parent.left) {
node.parent.left = replacement;
} else { // node == node.parent.right
node.parent.right = replacement;
}
} else if (node.parent == null) { // node是叶子节点并且是根节点
root = null;
} else { // node是叶子节点，但不是根节点
if (node == node.parent.left) {
node.parent.left = null;
} else { // node == node.parent.right
node.parent.right = null;
}
}
}
private Node<E> node(E element) {
Node<E> node = root;
while (node != null) {
int cmp = compare(element, node.element);
if (cmp == 0) return node;
if (cmp > 0) {
node = node.right;
} else { // cmp < 0
node = node.left;
}
}
return null;
}
// /**
// * 前序遍历
// */
// public void preorderTraversal() {
// preorderTraversal(root);
// }
//
// private void preorderTraversal(Node<E> node) {
// if (node == null) return;
//
// System.out.println(node.element);
// preorderTraversal(node.left);
// preorderTraversal(node.right);
// }
//
// /**
// * 中序遍历
// */
// public void inorderTraversal() {
// inorderTraversal(root);
// }
//
// private void inorderTraversal(Node<E> node) {
// if (node == null) return;
//
// inorderTraversal(node.left);
// System.out.println(node.element);
// inorderTraversal(node.right);
// }
//
// /**
// * 后序遍历
// */
// public void postorderTraversal() {
// postorderTraversal(root);
// }
//
// private void postorderTraversal(Node<E> node) {
// if (node == null) return;
//
// postorderTraversal(node.left);
// postorderTraversal(node.right);
// System.out.println(node.element);
// }
//
// /**
// * 层序遍历
// */
// public void levelOrderTraversal() {
// if (root == null) return;
//
// Queue<Node<E>> queue = new LinkedList<>();
// queue.offer(root);
//
// while (!queue.isEmpty()) {
// Node<E> node = queue.poll();
// System.out.println(node.element);
//
// if (node.left != null) {
// queue.offer(node.left);
// }
//
// if (node.right != null) {
// queue.offer(node.right);
// }
// }
// }
public void preorder(Visitor<E> visitor) {
if (visitor == null) return;
preorder(root, visitor);
}
private void preorder(Node<E> node, Visitor<E> visitor) {
if (node == null || visitor.stop) return;
visitor.stop = visitor.visit(node.element);
preorder(node.left, visitor);
preorder(node.right, visitor);
}
public void inorder(Visitor<E> visitor) {
if (visitor == null) return;
inorder(root, visitor);
}
private void inorder(Node<E> node, Visitor<E> visitor) {
if (node == null || visitor.stop) return;
inorder(node.left, visitor);
if (visitor.stop) return;
visitor.stop = visitor.visit(node.element);
inorder(node.right, visitor);
}
public void postorder(Visitor<E> visitor) {
if (visitor == null) return;
postorder(root, visitor);
}
private void postorder(Node<E> node, Visitor<E> visitor) {
if (node == null || visitor.stop) return;
postorder(node.left, visitor);
postorder(node.right, visitor);
if (visitor.stop) return;
visitor.stop = visitor.visit(node.element);
}
public void levelOrder(Visitor<E> visitor) {
if (root == null || visitor == null) return;
Queue<Node<E>> queue = new LinkedList<>();
queue.offer(root);
while (!queue.isEmpty()) {
Node<E> node = queue.poll();
if (visitor.visit(node.element)) return;
if (node.left != null) {
queue.offer(node.left);
}
if (node.right != null) {
queue.offer(node.right);
}
}
}
public boolean isComplete() {
if (root == null) return false;
Queue<Node<E>> queue = new LinkedList<>();
queue.offer(root);
boolean leaf = false;
while (!queue.isEmpty()) {
Node<E> node = queue.poll();
if (leaf && !node.isLeaf()) return false;
if (node.left != null) {
queue.offer(node.left);
} else if (node.right != null) { // node.left == null && node.right != null
return false;
}
if (node.right != null) {
queue.offer(node.right);
} else { // node.right == null
leaf = true;
}
}
return true;
}
// public boolean isComplete() {
// if (root == null) return false;
//
// Queue<Node<E>> queue = new LinkedList<>();
// queue.offer(root);
//
// boolean leaf = false;
// while (!queue.isEmpty()) {
// Node<E> node = queue.poll();
// if (leaf && !node.isLeaf()) return false;
//
// if (node.left != null && node.right != null) {
// queue.offer(node.left);
// queue.offer(node.right);
// } else if (node.left == null && node.right != null) {
// return false;
// } else { // 后面遍历的节点都必须是叶子节点
// leaf = true;
// if (node.left != null) {
// queue.offer(node.left);
// }
// }
// }
//
// return true;
// }
public int height() {
if (root == null) return 0;
// 树的高度
int height = 0;
// 存储着每一层的元素数量
int levelSize = 1;
Queue<Node<E>> queue = new LinkedList<>();
queue.offer(root);
while (!queue.isEmpty()) {
Node<E> node = queue.poll();
levelSize--;
if (node.left != null) {
queue.offer(node.left);
}
if (node.right != null) {
queue.offer(node.right);
}
if (levelSize == 0) { // 意味着即将要访问下一层
levelSize = queue.size();
height++;
}
}
return height;
}
public int height2() {
return height(root);
}
private int height(Node<E> node) {
if (node == null) return 0;
return 1 + Math.max(height(node.left), height(node.right));
}
@Override
public String toString() {
StringBuilder sb = new StringBuilder();
toString(root, sb, "");
return sb.toString();
}
private void toString(Node<E> node, StringBuilder sb, String prefix) {
if (node == null) return;
toString(node.left, sb, prefix + "L---");
sb.append(prefix).append(node.element).append("\n");
toString(node.right, sb, prefix + "R---");
}
/**
* @return 返回值等于0，代表e1和e2相等；返回值大于0，代表e1大于e2；返回值小于于0，代表e1小于e2
*/
private int compare(E e1, E e2) {
if (comparator != null) {
return comparator.compare(e1, e2);
}
return ((Comparable<E>)e1).compareTo(e2);
}
private void elementNotNullCheck(E element) {
if (element == null) {
throw new IllegalArgumentException("element must not be null");
}
}
@SuppressWarnings("unused")
private Node<E> predecessor(Node<E> node) {
if (node == null) return null;
// 前驱节点在左子树当中（left.right.right.right....）
Node<E> p = node.left;
if (p != null) {
while (p.right != null) {
p = p.right;
}
return p;
}
// 从父节点、祖父节点中寻找前驱节点
while (node.parent != null && node == node.parent.left) {
node = node.parent;
}
// node.parent == null
// node == node.parent.right
return node.parent;
}
private Node<E> successor(Node<E> node) {
if (node == null) return null;
// 前驱节点在左子树当中（right.left.left.left....）
Node<E> p = node.right;
if (p != null) {
while (p.left != null) {
p = p.left;
}
return p;
}
// 从父节点、祖父节点中寻找前驱节点
while (node.parent != null && node == node.parent.right) {
node = node.parent;
}
return node.parent;
}
public static abstract class Visitor<E> {
boolean stop;
/**
* @return 如果返回true，就代表停止遍历
*/
public abstract boolean visit(E element);
}
private static class Node<E> {
E element;
Node<E> left;
Node<E> right;
Node<E> parent;
public Node(E element, Node<E> parent) {
this.element = element;
this.parent = parent;
}
public boolean isLeaf() {
return left == null && right == null;
}
public boolean hasTwoChildren() {
return left != null && right != null;
}
}
@Override
public Object root() {
return root;
}
@Override
public Object left(Object node) {
return ((Node<E>)node).left;
}
@Override
public Object right(Object node) {
return ((Node<E>)node).right;
}
@Override
public Object string(Object node) {
Node<E> myNode = (Node<E>)node;
String parentString = "null";
if (myNode.parent != null) {
parentString = myNode.parent.element.toString();
}
return myNode.element + "_p(" + parentString + ")";
}
}
2.main函数
package com.mj;
import java.util.Comparator;
import com.mj.BinarySearchTree.Visitor;
import com.mj.file.Files;
import com.mj.printer.BinaryTreeInfo;
import com.mj.printer.BinaryTrees;
@SuppressWarnings("unused")
public class Main {
private static class PersonComparator implements Comparator<Person> {
public int compare(Person e1, Person e2) {
return e1.getAge() - e2.getAge();
}
}
private static class PersonComparator2 implements Comparator<Person> {
public int compare(Person e1, Person e2) {
return e2.getAge() - e1.getAge();
}
}
static void test1() {
Integer data[] = new Integer[] {
7, 4, 9, 2, 5, 8, 11, 3, 12, 1
};
BinarySearchTree<Integer> bst = new BinarySearchTree<>();
for (int i = 0; i < data.length; i++) {
bst.add(data[i]);
}
BinaryTrees.println(bst);
}
static void test2() {
Integer data[] = new Integer[] {
7, 4, 9, 2, 5, 8, 11, 3, 12, 1
};
BinarySearchTree<Person> bst1 = new BinarySearchTree<>();
for (int i = 0; i < data.length; i++) {
bst1.add(new Person(data[i]));
}
BinaryTrees.println(bst1);
BinarySearchTree<Person> bst2 = new BinarySearchTree<>(new Comparator<Person>() {
public int compare(Person o1, Person o2) {
return o2.getAge() - o1.getAge();
}
});
for (int i = 0; i < data.length; i++) {
bst2.add(new Person(data[i]));
}
BinaryTrees.println(bst2);
}
static void test3() {
BinarySearchTree<Integer> bst = new BinarySearchTree<>();
for (int i = 0; i < 40; i++) {
bst.add((int)(Math.random() * 100));
}
String str = BinaryTrees.printString(bst);
str += "\n";
Files.writeToFile("F:/1.txt", str, true);
// BinaryTrees.println(bst);
}
static void test4() {
BinaryTrees.println(new BinaryTreeInfo() {
@Override
public Object string(Object node) {
return node.toString() + "_";
}
@Override
public Object root() {
return "A";
}
@Override
public Object right(Object node) {
if (node.equals("A")) return "C";
if (node.equals("C")) return "E";
return null;
}
@Override
public Object left(Object node) {
if (node.equals("A")) return "B";
if (node.equals("C")) return "D";
return null;
}
});
// test3();
/*
* Java的匿名类，类似于iOS中的Block、JS中的闭包（function）
*/
// BinarySearchTree<Person> bst1 = new BinarySearchTree<>(new Comparator<Person>() {
// @Override
// public int compare(Person o1, Person o2) {
// return 0;
// }
// });
// bst1.add(new Person(12));
// bst1.add(new Person(15));
//
// BinarySearchTree<Person> bst2 = new BinarySearchTree<>(new PersonComparator());
// bst2.add(new Person(12));
// bst2.add(new Person(15));
//
// BinarySearchTree<Car> bst4 = new BinarySearchTree<>(new Car);
//
//
// java.util.Comparator<Integer> iComparator;
}
static void test5() {
BinarySearchTree<Person> bst = new BinarySearchTree<>();
bst.add(new Person(10, "jack"));
bst.add(new Person(12, "rose"));
bst.add(new Person(6, "jim"));
bst.add(new Person(10, "michael"));
BinaryTrees.println(bst);
}
static void test6() {
Integer data[] = new Integer[] {
7, 4, 9, 2, 5
};
BinarySearchTree<Integer> bst = new BinarySearchTree<>();
for (int i = 0; i < data.length; i++) {
bst.add(data[i]);
}
// BinarySearchTree<Integer> bst = new BinarySearchTree<>();
// for (int i = 0; i < 10; i++) {
// bst.add((int)(Math.random() * 100));
// }
BinaryTrees.println(bst);
System.out.println(bst.isComplete());
// bst.levelOrderTraversal();
/*
* 7
* 4 9
2 5
*/
// bst.levelOrder(new Visitor<Integer>() {
// public void visit(Integer element) {
// System.out.print("_" + element + "_ ");
// }
// });
// bst.inorder(new Visitor<Integer>() {
// public void visit(Integer element) {
// System.out.print("_" + (element + 3) + "_ ");
// }
// });
// System.out.println(bst.height());
}
static void test7() {
Integer data[] = new Integer[] {
7, 4, 9, 2, 5, 8, 11, 3, 12, 1
};
BinarySearchTree<Integer> bst = new BinarySearchTree<>();
for (int i = 0; i < data.length; i++) {
bst.add(data[i]);
}
BinaryTrees.println(bst);
bst.remove(7);
BinaryTrees.println(bst);
}
static void test8() {
Integer data[] = new Integer[] {
7, 4, 9, 2, 1
};
BinarySearchTree<Integer> bst = new BinarySearchTree<>();
for (int i = 0; i < data.length; i++) {
bst.add(data[i]);
}
BinaryTrees.println(bst);
System.out.println(bst.isComplete());
}
static void test9() {
Integer data[] = new Integer[] {
7, 4, 9, 2, 1
};
BinarySearchTree<Integer> bst = new BinarySearchTree<>();
for (int i = 0; i < data.length; i++) {
bst.add(data[i]);
}
BinaryTrees.println(bst);
bst.preorder(new Visitor<Integer>() {
public boolean visit(Integer element) {
System.out.print(element + " ");
return element == 2 ? true : false;
}
});
System.out.println();
bst.inorder(new Visitor<Integer>() {
public boolean visit(Integer element) {
System.out.print(element + " ");
return element == 4 ? true : false;
}
});
System.out.println();
bst.postorder(new Visitor<Integer>() {
public boolean visit(Integer element) {
System.out.print(element + " ");
return element == 4 ? true : false;
}
});
System.out.println();
bst.levelOrder(new Visitor<Integer>() {
public boolean visit(Integer element) {
System.out.print(element + " ");
return element == 9 ? true : false;
}
});
System.out.println();
}
public static void main(String[] args) {
test9();
}
}
3.Person类
package com.mj;
public class Person implements Comparable<Person> {
private int age;
private String name;
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public Person(int age) {
this.age = age;
}
public Person(int age, String name) {
this.age = age;
this.name = name;
}
@Override
public int compareTo(Person e) {
// if (age > e.age) return 1;
// if (age < e.age) return -1;
// return 0;
return age - e.age;
}
@Override
public String toString() {
return age + "_" + name;
}
}
来源：https://www.cnblogs.com/ggnbnb/p/12287092.html