二叉树的前序遍历，中序遍历，后序遍历（递归的写法）
///////////////////////////////////递归////////////////////////////////////////////////////////
//下面先构建树的类
package facehandjava.tree;
public class Node {
private int data;
private Node leftNode;
private Node rightNode;
public Node(int data, Node leftNode, Node rightNode){
this.data = data;
this.leftNode = leftNode;
this.rightNode = rightNode;
}
public int getData() {
return data;
}
public void setData(int data) {
this.data = data;
}
public NodegetLeftNode() {
return leftNode;
}
public void setLeftNode(Node leftNode) {
this.leftNode = leftNode;
}
public NodegetRightNode() {
return rightNode;
}
public void setRightNode(Node rightNode) {
this.rightNode = rightNode;
}
}
package facehandjava.tree;
public class RecursiveBinaryTree {
/**
*
* 二叉树的先序中序后序排序（递归版本）
*/
public Node init() {//注意必须逆序建立，先建立子节点，再逆序往上建立，因为非叶子结点会使用到下面的节点，而初始化是按顺序初始化的，不逆序建立会报错
Node J = new Node(8, null, null);
Node H = new Node(4, null, null);
Node G = new Node(2, null, null);
Node F = new Node(7, null, J);
Node E = new Node(5, H, null);
Node D = new Node(1, null, G);
Node C = new Node(9, F, null);
Node B = new Node(3, D, E);
Node A = new Node(6, B, C);
return A; //返回根节点
}
public static void main(String[] args) {
RecursiveBinaryTree tree = new RecursiveBinaryTree();
Node root = tree.init();
System.out.println("先序遍历(递归)");
tree.FirstTraversal(root);
System.out.println("");
System.out.println("中序遍历(递归)");
tree.MiddleTraversal(root);
System.out.println("");
System.out.println("后序遍历(递归)");
tree.LastTraversal(root);
System.out.println("");
}
private void FirstTraversal(Node root) {
System.out.print(root.getData());
if (root.getLeftNode()!= null) {
FirstTraversal(root.getLeftNode());
}
if (root.getRightNode()!= null) {
FirstTraversal(root.getRightNode());
}
}
private void MiddleTraversal(Node root) {
if (root.getLeftNode()!= null) {
MiddleTraversal(root.getLeftNode());
}
System.out.print(root.getData());
if (root.getRightNode()!= null) {
MiddleTraversal(root.getRightNode());
}
}
private void LastTraversal(Node root) {
if (root.getLeftNode()!= null) {
LastTraversal(root.getLeftNode());
}
if (root.getRightNode()!= null) {
LastTraversal(root.getRightNode());
}
System.out.print(root.getData());
}
}
///////////////////////////////////非递归////////////////////////////////////////////////////////
//下面先构建树的类
package facehandjava.tree;
public class Node {
private int data;
private Node leftNode;
private Node rightNode;
public Node(int data, Node leftNode, Node rightNode){
this.data = data;
this.leftNode = leftNode;
this.rightNode = rightNode;
}
public int getData() {
return data;
}
public void setData(int data) {
this.data = data;
}
public NodegetLeftNode() {
return leftNode;
}
public void setLeftNode(Node leftNode) {
this.leftNode = leftNode;
}
public NodegetRightNode() {
return rightNode;
}
public void setRightNode(Node rightNode) {
this.rightNode = rightNode;
}
}
package facehandjava.tree;
import java.util.ArrayList;
import java.util.List;
import java.util.Stack;
public class NonRecursiveBinaryTree {
/**
* 二叉树的先序中序后序排序（非递归版本）
*/
public Node init() {//注意必须逆序建立，先建立子节点，再逆序往上建立，因为非叶子结点会使用到下面的节点，而初始化是按顺序初始化的，不逆序建立会报错
Node J = new Node(8, null, null);
Node H = new Node(4, null, null);
Node G = new Node(2, null, null);
Node F = new Node(7, null, J);
Node E = new Node(5, H, null);
Node D = new Node(1, null, G);
Node C = new Node(9, F, null);
Node B = new Node(3, D, E);
Node A = new Node(6, B, C);
return A; //返回根节点
}
public static void main(String[] args) {
NonRecursiveBinaryTree tree =new NonRecursiveBinaryTree();
Node root = tree.init();
System.out.println("先序遍历(应该)\n" +
"631254978\n" +
"中序遍历(应该)\n" +
"123456789\n" +
"后序遍历(应该)\n" +
"214538796");
System.out.println("先序遍历(非递归)");
FirstTraversal_Stack(root);
System.out.println("");
System.out.println("中序遍历(非递归)");
MiddleTraversal_Stack(root);
System.out.println("");
System.out.println("后序遍历(非递归)");
LastTraversal_Stack(root);
System.out.println("");
}
private static void FirstTraversal_Stack(Node root) {
Stack<Node> stack = new Stack<>();
while (root!= null || !stack.isEmpty()) {
if (root!= null) {
System.out.print(root.getData());
stack.push(root);
root =root.getLeftNode();
} else {
root = stack.pop();
root =root.getRightNode();
}
}
}
private static void MiddleTraversal_Stack(Node root) {
Stack<Node> stack = new Stack<>();
while (root!= null || !stack.isEmpty()) {
if (root!=null) {
stack.push(root);
root =root.getLeftNode();
} else {
root = stack.pop();
System.out.print(root.getData());
root =root.getRightNode();
}
}
}
private static void LastTraversal_Stack(Node root) {
Stack<Node> stack = new Stack<>();
Stack<Node> out = new Stack<>();
while (root!= null || !stack.isEmpty()) {
if (root!= null) {
out.push(root);
stack.push(root);
root =root.getRightNode();
} else {
root = stack.pop();
root =root.getLeftNode();
}
}
while (!out.isEmpty()){
System.out.print(out.pop().getData());
}
}
}