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src/main/java/cn/byhieg/algorithmtutorial/BinarySearchTree.java
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package cn.byhieg.algorithmtutorial; | ||
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/** | ||
* Created by byhieg on 17/3/30. | ||
* Mail to byhieg@gmail.com | ||
*/ | ||
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import java.util.Stack; | ||
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/** | ||
* 该类是二叉搜索树 | ||
* 该树在实现的时候,不考虑数组中有重复的数字。 | ||
* 节点的左子节点的值都小于这个节点的值,节点的右子节点的值都大于等于这个节点的值 | ||
*/ | ||
public class BinarySearchTree { | ||
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private Node root; | ||
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public BinarySearchTree(){ | ||
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} | ||
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public BinarySearchTree(int[] nums) { | ||
Node[] nodes = new Node[nums.length]; | ||
for (int i = 0 ; i < nums.length;i++) { | ||
nodes[i] = new Node(nums[i]); | ||
insert(nodes[i]); | ||
} | ||
} | ||
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/** | ||
* 查找指定的元素 | ||
* @param des | ||
* @return | ||
*/ | ||
public Node find(int des){ | ||
if (root == null) { | ||
System.out.println("树是空的"); | ||
throw new RuntimeException(); | ||
} | ||
Node current = root; | ||
while (current.data != des) { | ||
if (current.data < des) { | ||
current = current.right; | ||
}else{ | ||
current = current.left; | ||
} | ||
if (current == null) return null; | ||
} | ||
return current; | ||
} | ||
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/** | ||
* 对BST执行插入操作,采用非递归的形式 | ||
* 保证插入后,左节点的值小于根节点的值,根节点的值小于右节点的值 | ||
* @param node | ||
* @return | ||
*/ | ||
public boolean insert(Node node){ | ||
if (root == null) { | ||
root = node; | ||
return true; | ||
} | ||
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if (find(node.data) != null) { | ||
System.out.println("不允许插入相同data的数"); | ||
throw new RuntimeException(); | ||
} | ||
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Node current = root; | ||
while (current != null) { | ||
if (current.data < node.data) { | ||
if (current.right == null) { | ||
current.right = node; | ||
return true; | ||
} | ||
current = current.right; | ||
}else{ | ||
if (current.left == null) { | ||
current.left = node; | ||
return true; | ||
} | ||
current = current.left; | ||
} | ||
} | ||
return false; | ||
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} | ||
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/** | ||
* 树的前序遍历,递归实现 | ||
*/ | ||
public void preOrder(Node node) { | ||
System.out.print(node.data + "-->"); | ||
if (node.left != null) { | ||
preOrder(node.left); | ||
} | ||
if (node.right != null) { | ||
preOrder(node.right); | ||
} | ||
} | ||
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/** | ||
* 树的中序遍历,递归实现 | ||
* 针对BST,该结果会从小到大输出树 | ||
* @param node | ||
*/ | ||
public void inOrder(Node node){ | ||
if (node.left != null) { | ||
inOrder(node.left); | ||
} | ||
System.out.print(node.data + "-->"); | ||
if (node.right != null) { | ||
inOrder(node.right); | ||
} | ||
} | ||
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/** | ||
* 树的后续遍历,递归实现 | ||
*/ | ||
public void postOrder(Node node){ | ||
if (node.left != null) { | ||
postOrder(node.left); | ||
} | ||
if (node.right != null) { | ||
postOrder(node.right); | ||
} | ||
System.out.print(node.data + "-->"); | ||
} | ||
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/** | ||
* 树的先续遍历,非递归实现 | ||
* 1. 建立一个栈,现将头结点压入栈中。 | ||
* 2. 现将每出栈一个节点,打印他的值,然后都要先加入他的右节点,在加入他的左节点。因为栈的后进先出的特性,才能让左边先出。 | ||
* 3. 不断重复2,直到栈空 | ||
* | ||
*/ | ||
public void preOrder2(Node node) { | ||
if (node != null) { | ||
Stack<Node> stack = new Stack<>(); | ||
stack.push(node); | ||
while (!stack.isEmpty()) { | ||
Node tmp = stack.pop(); | ||
System.out.print(tmp.data + "-->"); | ||
if (tmp.right != null) { | ||
stack.push(tmp.right); | ||
} | ||
if (tmp.left != null) { | ||
stack.push(tmp.left); | ||
} | ||
} | ||
} | ||
} | ||
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/** | ||
* 树的中序遍历,非递归实现 | ||
* 1. 设定cur,初始化cur = root节点,不断遍历里cur.left,并将其压入栈中,直到null。 | ||
* 2. 出栈一个节点,打印他的值,然后cur = node.right,并不断重复第二步 | ||
* 3. 当栈为空,并且cur为空时,停止 | ||
*/ | ||
public void inorder2(Node node){ | ||
if (node != null) { | ||
Stack<Node> stack = new Stack<>(); | ||
Node cur = node; | ||
while (!stack.isEmpty() || cur != null) { | ||
if (cur == null) { | ||
cur = stack.pop(); | ||
System.out.print(cur.data + "-->"); | ||
cur = cur.right; | ||
}else{ | ||
stack.push(cur); | ||
cur = cur.left; | ||
} | ||
} | ||
} | ||
} | ||
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/** | ||
* 树的后续遍历,非递归实现 | ||
* 1. 树的先续遍历中,是栈存放顺序是根,右节点,左节点。 | ||
* 2. 我们可以将其反过来,用栈存放是根,左节点,右节点。然后出栈的时候,将出栈的结果存放到另一个栈里。 | ||
* 3. 第二栈里的顺序从上到下就是左节点,右节点,根的顺序。 | ||
* @param node | ||
*/ | ||
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public void postOrder2(Node node) { | ||
if (node != null) { | ||
Stack<Node> stack = new Stack<>(); | ||
Stack<Node> result = new Stack<>(); | ||
Node cur = node; | ||
stack.push(cur); | ||
while (!stack.isEmpty()){ | ||
Node tmp = stack.pop(); | ||
result.push(tmp); | ||
if (tmp.left != null) { | ||
stack.push(tmp.left); | ||
} | ||
if (tmp.right != null) { | ||
stack.push(tmp.right); | ||
} | ||
} | ||
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while (!result.isEmpty()) { | ||
System.out.print(result.pop().data + "-->"); | ||
} | ||
} | ||
} | ||
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/** | ||
* 得到树中最小的节点 | ||
* @return | ||
*/ | ||
public Node getMinNode(){ | ||
if (root == null) { | ||
throw new RuntimeException("树为空"); | ||
} | ||
Node current = root; | ||
while (current.left != null) { | ||
current = current.left; | ||
} | ||
return current; | ||
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} | ||
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/** | ||
* 得到树中最大的节点 | ||
* @return | ||
*/ | ||
public Node getMaxNode(){ | ||
if (root == null) { | ||
throw new RuntimeException("树为空"); | ||
} | ||
Node current = root; | ||
while (current.right != null) { | ||
current = current.right; | ||
} | ||
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return current; | ||
} | ||
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public static class Node{ | ||
public int data; | ||
public Node left; | ||
public Node right; | ||
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public Node(int data){ | ||
this.data = data; | ||
} | ||
} | ||
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public Node getRoot() { | ||
return root; | ||
} | ||
} |
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src/test/java/cn/byhieg/collectiontutorialtest/BinarySearchTreeTest.java
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package cn.byhieg.collectiontutorialtest; | ||
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import cn.byhieg.algorithmtutorial.BinarySearchTree; | ||
import com.sun.tools.internal.ws.wsdl.document.soap.SOAPUse; | ||
import junit.framework.TestCase; | ||
import org.junit.Assert; | ||
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/** | ||
* Created by byhieg on 17/3/30. | ||
* Mail to byhieg@gmail.com | ||
*/ | ||
public class BinarySearchTreeTest extends TestCase { | ||
int [] nums; | ||
BinarySearchTree tree; | ||
public void setUp() throws Exception { | ||
super.setUp(); | ||
nums = new int[]{10,6,2,8,7,3,4,1}; | ||
tree = new BinarySearchTree(nums); | ||
} | ||
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public void tearDown() throws Exception { | ||
} | ||
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public void testInsert() throws Exception { | ||
} | ||
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public void testInOrder() throws Exception { | ||
System.out.println("中序遍历"); | ||
tree.inorder2(tree.getRoot()); | ||
System.out.println(); | ||
} | ||
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public void testPreOrder() throws Exception { | ||
System.out.println("先续遍历"); | ||
tree.preOrder2(tree.getRoot()); | ||
System.out.println(); | ||
} | ||
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public void testPostOrder() throws Exception { | ||
System.out.println("后续遍历"); | ||
tree.postOrder2(tree.getRoot()); | ||
System.out.println(); | ||
} | ||
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public void testGetMaxData() throws Exception { | ||
// Assert.assertEquals(12,tree.getMaxNode().data); | ||
} | ||
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public void testGetMinData() throws Exception { | ||
// Assert.assertEquals(1,tree.getMinNode().data); | ||
} | ||
} |