二叉树的镜像

来源：互联网发布：美国p2p软件编辑：程序博客网时间：2024/05/19 16:05

题目:请完成一个函数，输入一个二叉树，该函数输出它的镜像。

所谓数的镜像，就是指每个节点的左右子节点互换位置。列如一棵二叉树的先序遍历为：8 6 5 7 10 9 11，它的镜像树的先序遍历则为8 10 11 9 6 7 5 。

代码如下：

       public class BinaryTreeDemo {

   public static void main(String[] args) {
       /**
       * 构造一棵二叉树
       * */
       BinaryTreeNode root = new BinaryTreeNode(8);
       root.left = new BinaryTreeNode(6);
       root.right = new BinaryTreeNode(10);

       root.left.left = new BinaryTreeNode(5);
       root.left.right = new BinaryTreeNode(7);

       root.right.left = new BinaryTreeNode(9);
       root.right.right = new BinaryTreeNode(11);

       root.left.left.left = null;
       root.left.left.right = null;

       root.left.right.left = null;
       root.left.right.right = null;

       root.right.left.left = null;
       root.right.left.right = null;

       root.right.right.left = null;
       root.right.right.right = null;

       /**
       * 先序遍历二叉树
       * */
       printBinaryTree(root);
       System.out.println();
       /**
       * 求出一棵二叉树的镜像
       *
       * */
       BinaryTreeNode root1 = mirrorRecursively(root);
       printBinaryTree(root1);

   }

   private static BinaryTreeNode mirrorRecursively(BinaryTreeNode root) {
       if(root != null){
           BinaryTreeNode treeNode = null;
           //调换节点的左右节点
           treeNode = root.left;
           root.left = root.right;
           root.right = treeNode;
           root.left = mirrorRecursively(root.left);
           root.right = mirrorRecursively(root.right);
       }else{
           return null;
       }
       return root;
   }

   private static void printBinaryTree(BinaryTreeNode root) {
       if(root != null){

           System.out.print(root.value + " ");
           printBinaryTree(root.left);
           printBinaryTree(root.right);

       }else{
           return;
       }


   }

}
/**
*
*二叉树的节点类
* */
class BinaryTreeNode{
   public int value;
   public BinaryTreeNode left;
   public BinaryTreeNode right;

   public BinaryTreeNode(int value) {
       super();
       this.value = value;
   }

   public BinaryTreeNode() {
       super();
   }


}

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