java 二叉树的镜像

题目

二叉树的镜像定义：

源二叉树
8
/  \
6   10
/ \  / \
5  7 9 11

镜像二叉树
8
/  \
10   6
/ \  / \
11 9 7  5

思路

代码

import java.util.Stack;
import java.util.LinkedList;
class TreeNode {
int val = 0;
TreeNode left = null;
TreeNode right = null;

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

public class Main {
//递归
public static void Mirror(TreeNode root) {
if (root == null)
return;
if (root.left == null && root.right == null)
return;
TreeNode temp = root.left;
root.left = root.right;
root.right = temp;
if(root.left!=null) Mirror(root.left);
if(root.right!=null) Mirror(root.right);
}
//非递归
public static void MirrorN(TreeNode root){
if(root==null) return;
Stack<TreeNode> stack=new Stack<TreeNode>();
stack.push(root);
while(!stack.isEmpty()){
TreeNode node = stack.pop();
if(node.left!=null||node.right!=null){
TreeNode temp = node.left;
node.left = node.right;
node.right = temp;
}
if(node.left!=null){
stack.push(node.left);
}
if(node.right!=null){
stack.push(node.right);
}
}
}
//层序遍历二叉树
public static void levelTraverse(TreeNode root){
LinkedList<TreeNode> list= new LinkedList<TreeNode>();
list.add(root);
while(list.size() != 0){
TreeNode node = list.removeFirst();
System.out.print(node.val + " ");
if(node.left != null){
list.add(node.left);
}
if(node.right != null){
list.add(node.right);
}
}
}
public static void main(String[] args) {
// TODO Auto-generated method stub
TreeNode root = new TreeNode(8);
TreeNode a=new TreeNode(6);
TreeNode b=new TreeNode(10);
TreeNode aa=new TreeNode(5);
TreeNode ab=new TreeNode(7);
TreeNode ba=new TreeNode(9);
TreeNode bb=new TreeNode(11);

root.left=a;
root.right=b;
a.left=aa;
a.right=ab;
b.left=ba;
b.right=bb;
levelTraverse(root);
MirrorN(root);
System.out.println();
levelTraverse(root);
}
}

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