27 二叉搜索树与双向链表

package question27;

import java.util.ArrayList;
import java.util.Scanner;

class TreeNode {
int val = 0;
TreeNode left = null;
TreeNode right = null;

public TreeNode(int val) {
this.val = val;

}

}
public class ConvertBinarySearchTree {
// 方法一   思路是先根据中序遍历把每个节点保存到列表中，然后变成右连得单链表，最后变成左连得单链表
/*public TreeNode Convert(TreeNode pRootOfTree) {

ArrayList<TreeNode> list=new ArrayList<TreeNode>();
recursive (pRootOfTree,list);
for (int i = 0; i < list.size(); i++) {
System.out.print(list.get(i).val+" ");
}
getRightLinkedList (list);
getLeftLinkedList(list);

return pRootOfTree;
}*/

// 方法二 是剑指 Offer 给的答案，思路是:  原先指向左结点的指针调整为链表中指向前一个结点的指针，原先指向右结点的指针调整为链表中指向后一个结点的指针
TreeNode pLastNodeInList=null;
public TreeNode Convert(TreeNode pRootOfTree) {

ConvertNode(pRootOfTree);

TreeNode pHeadOfList=pLastNodeInList;
while (pHeadOfList!=null&&pHeadOfList.left!=null) {
pHeadOfList=pHeadOfList.left;
}
return pHeadOfList;
}

private void ConvertNode(TreeNode pNode) {
// TODO Auto-generated method stub
if (pNode==null) {
return ;
}
//
TreeNode pCurrent=pNode;
if (pCurrent.left!=null) {
ConvertNode(pCurrent.left);
}

//
pCurrent.left=pLastNodeInList;
if (pLastNodeInList!=null) {
pLastNodeInList.right=pCurrent;
}
pLastNodeInList=pCurrent;

//
if (pCurrent.right!=null) {
ConvertNode(pCurrent.right);
}

}
private void getLeftLinkedList(ArrayList<TreeNode> list) {
// TODO Auto-generated method stub
if (list==null||list.size()==0) {
return;
}
for (int i =list.size()-1; i >0; i--) {
list.get(i).left=list.get(i-1);
}
list.get(0).left=null;
}
private void getRightLinkedList(ArrayList<TreeNode> list) {
// TODO Auto-generated method stub
if (list==null||list.size()==0) {
return;
}
for (int i = 0; i < list.size()-1; i++) {

list.get(i).right=list.get(i+1);

}
list.get(list.size()-1).right=null;
}
private void recursive(TreeNode pRootOfTree, ArrayList<TreeNode> list) {
// TODO Auto-generated method stub
if (pRootOfTree!=null) {
recursive(pRootOfTree.left, list);
list.add(pRootOfTree);
recursive(pRootOfTree.right, list);
}

}
public static void main(String[] args) {
// TODO Auto-generated method stub

Scanner in=new Scanner(System.in);

System.out.println("请输入树 的先序遍历:");
TreeNode root=creatTree(in);
System.out.println("下面是树 的先序遍历:");
display(root);
System.out.println();
ConvertBinarySearchTree ly=new ConvertBinarySearchTree();

root=ly.Convert(root);
System.out.println("左到右:");
displayLeft(root);
System.out.println("\n右到左:");
displayRight(root);

}

// 右到左显示
private static void displayRight(TreeNode root) {
// TODO Auto-generated method stub
if (root!=null) {

displayRight(root.right);
System.out.print(root.val+" ");
}
}

// 左到右显示
private static void displayLeft(TreeNode root) {
// TODO Auto-generated method stub
if (root!=null) {
System.out.print(root.val+" ");
displayLeft(root.right);
}
}
// 创建二叉树
private static TreeNode creatTree(Scanner in) {
// TODO Auto-generated method stub
TreeNode newNode;
int val=in.nextInt();
if (val==-1) {     //设置 -1 为结束数字
val=in.nextInt();
}
if (val!=0) {    // 0 代表空节点
newNode=new TreeNode(val);
}else {
newNode=null;
return null;
}

newNode.left=creatTree(in);
newNode.right=creatTree(in);

return newNode;

}
// 打印二叉树
private static void display(TreeNode root) {
// TODO Auto-generated method stub

if (root!=null) {
System.out.print(root.val+"  ");
display( root.left);
display(root.right);

}
}
}