java编程基础——二叉树的镜像

题目描述

操作给定的二叉树，将其变换为源二叉树的镜像。

题目代码

/**
 * @program: JavaCode
 * @description: 操作给定的二叉树，将其变换为源二叉树的镜像。
 * 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
 * @author: Yukai Fan
 * @create: 2018-09-04 21:51
 **/
public class MirrorTree {
    public static void main(String[] args) {
        TreeNode tree = new TreeNode(8);
        tree.left = new TreeNode(6);
        tree.left.left = new TreeNode(5);
        tree.left.right = new TreeNode(7);
        tree.right = new TreeNode(10);
        tree.right.left = new TreeNode(9);
        tree.right.right = new TreeNode(11);
        TreeNode mirror = Mirror(tree);
        System.out.println(mirror);
    }
    /*
    先前序遍历这棵树的每个结点，如果遍历到的结点有子结点，就交换它的两个子节点，
    当交换完所有的非叶子结点的左右子结点之后，就得到了树的镜像
    */
    public static TreeNode Mirror(TreeNode tree) {
        if (tree == null) {
            return null;
        }
        if (tree.left == null && tree.right == null) {
            return null;
        }
        TreeNode mirrorTree = tree.left;
        tree.left = tree.right;
        tree.right = mirrorTree;

        if (tree.left != null) {
            Mirror(tree.left);
        }
        if (tree.right != null) {
            Mirror(tree.right);
        }

        return tree;

    }

}

/**
 * @program: JavaCode
 * @description: 创建二叉树
 * @author: Yukai Fan
 * @create: 2018-09-04 21:52
 **/
public class TreeNode {
    int val;
    TreeNode left = null;
    TreeNode right = null;
    public TreeNode(int val) {
        this.val = val;
    }
}