首先我想问为什么要用LinkedList 来建立二叉树呢? LinkedList 是线性表,
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树是树形的, 似乎不太合适。
其实也可以用数组完成，而且效率更凳备高.
关键是我觉得你这个输入本身就是一迟掘个二叉树啊，
String input = "ABCDE F G";
节点编号从0到8. 层次遍历的话:
对于节点i.
leftChild = input.charAt(2*i+1); //做子树
rightChild = input.charAt(2*i+2);//右子树
如果你要将带有节点信息的树存到LinkedList里面, 先建立一个节点类:
class Node{
public char cValue;
public Node leftChild;
public Node rightChild;
public Node(v){
this.cValue = v;
}
}
然后遍历input,建立各个节点对象.
LinkedList tree = new LinkedList();
for(int i=0;i input.length;i++)
LinkedList.add(new Node(input.charAt(i)));
然后为各个节点设置左右子树:
for(int i=0;iinput.length;i++){
((Node)tree.get(i)).leftChild = (Node)tree.get(2*i+1);
((Node)tree.get(i)).rightChild = (Node)tree.get(2*i+2);
}
这样LinkedList 就存储了整个二叉树码粗核. 而第0个元素就是树根，思路大体是这样吧。
二叉树的相关操作，包括创建，中序、先序、后序（递归和非递归），碧闭知其中重态谨点的是java在先序创建二叉树和后序非递归遍历的的实现悔消。
package com.algorithm.tree;
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Queue;
import java.util.Scanner;
import java.util.Stack;
import java.util.concurrent.LinkedBlockingQueue;
public class Tree {
private Node root;
public Tree() {
}
public Tree(Node root) {
this.root = root;
}
//创建二叉树
public void buildTree() {
Scanner scn = null;
try {
scn = new Scanner(new File("input.txt"));
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
root = createTree(root,scn);
}
//先序遍历创建二叉树
private Node createTree(Node node,Scanner scn) {
String temp = scn.next();
if (temp.trim().equals("#")) {
return null;
} else {
node = new Node((T)temp);
node.setLeft(createTree(node.getLeft(), scn));
node.setRight(createTree(node.getRight(), scn));
return node;
}
}
//中序遍历(递归)
public void inOrderTraverse() {
inOrderTraverse(root);
}
public void inOrderTraverse(Node node) {
if (node != null) {
inOrderTraverse(node.getLeft());
System.out.println(node.getValue());
inOrderTraverse(node.getRight());
}
}
//中序遍历(非递归)
public void nrInOrderTraverse() {
StackNode stack = new StackNode();
Node node = root;
while (node != null || !stack.isEmpty()) {
while (node != null) {
stack.push(node);
node = node.getLeft();
}
node = stack.pop();
System.out.println(node.getValue());
node = node.getRight();
}
}
//先序遍历(递归)
public void preOrderTraverse() {
preOrderTraverse(root);
}
public void preOrderTraverse(Node node) {
if (node != null) {
System.out.println(node.getValue());
preOrderTraverse(node.getLeft());
preOrderTraverse(node.getRight());
}
}
//先序遍历（非递归）
public void nrPreOrderTraverse() {
StackNode stack = new StackNode();
Node node = root;
while (node != null || !stack.isEmpty()) {
while (node != null) {
System.out.println(node.getValue());
stack.push(node);
node = node.getLeft();
}
node = stack.pop();
node = node.getRight();
}
}
//后序遍历(递归)
public void postOrderTraverse() {
postOrderTraverse(root);
}
public void postOrderTraverse(Node node) {
if (node != null) {
postOrderTraverse(node.getLeft());
postOrderTraverse(node.getRight());
System.out.println(node.getValue());
}
}
//后续遍历(非递归)
public void nrPostOrderTraverse() {
StackNode stack = new StackNode();
Node node = root;
Node preNode = null;//表示最近一次访问的节点
while (node != null || !stack.isEmpty()) {
while (node != null) {
stack.push(node);
node = node.getLeft();
}
node = stack.peek();
if (node.getRight() == null || node.getRight() == preNode) {
System.out.println(node.getValue());
node = stack.pop();
preNode = node;
node = null;
} else {
node = node.getRight();
}
}
}
//按层次遍历
public void levelTraverse() {
levelTraverse(root);
}
public void levelTraverse(Node node) {
QueueNode queue = new LinkedBlockingQueueNode();
queue.add(node);
while (!queue.isEmpty()) {
Node temp = queue.poll();
if (temp != null) {
System.out.println(temp.getValue());
queue.add(temp.getLeft());
queue.add(temp.getRight());
}
}
}
}
//树的节点
class Node {
private Node left;
private Node right;
private T value;
public Node() {
}
public Node(Node left,Node right,T value) {
this.left = left;
this.right = right;
this.value = value;
}
public Node(T value) {
this(null,null,value);
}
public Node getLeft() {
return left;
}
public void setLeft(Node left) {
this.left = left;
}
public Node getRight() {
return right;
}
public void setRight(Node right) {
this.right = right;
}
public T getValue() {
return value;
}
public void setValue(T value) {
this.value = value;
}
}
测试代码：
package com.algorithm.tree;
public class TreeTest {
/**
* @param args
*/
public static void main(String[] args) {
Tree tree = new Tree();
tree.buildTree();
System.out.println("中序遍历");
tree.inOrderTraverse();
tree.nrInOrderTraverse();
System.out.println("后续遍历");
//tree.nrPostOrderTraverse();
tree.postOrderTraverse();
tree.nrPostOrderTraverse();
System.out.println("先序遍历");
tree.preOrderTraverse();
tree.nrPreOrderTraverse();
//
}
}
import java.util.List;
import java.util.LinkedList;
public class Bintrees {
private int[] array = {1, 2, 3, 4, 5, 6, 7, 8, 9};
private static ListNode nodeList = null;
private static class Node {
Node leftChild;
Node rightChild;
int data;
Node(int newData) {
leftChild = null;
rightChild = null;
data = newData;
}
}
// 创建二叉树
public void createBintree() {
nodeList = new LinkedListNode();
// 将数组的值转换为node
for (int nodeIndex = 0; nodeIndex array.length; nodeIndex++) {
nodeList.add(new Node(array[nodeIndex]));
}
// 对除最后一个父节点按照父节点和孩子节点的数字关系建立二叉树
for (int parentIndex = 0; parentIndex array.length / 2 - 1; parentIndex++) {
nodeList.get(parentIndex).leftChild = nodeList.get(parentIndex * 2 + 1);
nodeList.get(parentIndex).rightChild = nodeList.get(parentIndex * 2 + 2);
}
//嫌掘 最后一个父节点哪者咐
int lastParentIndex = array.length / 2 - 1;
// 左孩子
nodeList.get(lastParentIndex).leftChild = nodeList.get(lastParentIndex * 2 + 1);
// 如果为奇数，建立右孩子
if (array.length % 2 == 1) {
nodeList.get(lastParentIndex).rightChild = nodeList.get(lastParentIndex * 2 + 2);
}
}
// 前序遍历
public static void preOrderTraverse(Node node) {
if (node == null) {
return;
}
System.out.print(node.data + " ");
preOrderTraverse(node.leftChild);
preOrderTraverse(node.rightChild);
}
// 中序遍历
public static void inOrderTraverse(Node node) {
if (node == null) {
return;
}
inOrderTraverse(node.leftChild);
System.out.print(node.data + " ");
inOrderTraverse(node.rightChild);
}
// 后序遍历
public static void postOrderTraverse(Node node) {
if (node == null) {
return;
}
postOrderTraverse(node.leftChild);
postOrderTraverse(node.rightChild);
System.out.print(node.data + " ");
}
public static void main(String[] args) {
Bintrees binTree = new Bintrees();
binTree.createBintree();
Node root = nodeList.get(0);
System.out.println("前序遍李纯历：");
preOrderTraverse(root);
System.out.println();
System.out.println("中序遍历：");
inOrderTraverse(root);
System.out.println();
System.out.println("后序遍历：");
postOrderTraverse(root);
}
}
输出结果：
前序遍历：
1 2 4 8 9 5 3 6 7
中序遍历：
8 4 9 2 5 1 6 3 7
后序遍历：
8 9 4 5 2 6 7 3 1
