Sword refers to offer: Face Test 19--Two-fork Tree mirroring (Java implementation)

Source: Internet
Author: User

Problem Description:

Operates the given two-fork tree and transforms it into a mirror of the source binary tree. The binary tree node is defined as:

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

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



For example:

       /  \
     /\  /\
    5  7 9 One
    mirror binary tree
      ten   6
     /\  /\
    9 7  5


Starting from the root node, recursive, first swap the left and right subtree, and then transform the left and right subtree to its mirror image.


public void Mirror (TreeNode root) {

        if (root = null) {return

        if (Root.left = = NULL && Root.right = null) {return

        TreeNode tmp = Root.left;
        Root.left = root.right;
        Root.right = tmp;

        if (root.left!= null) {//Here the null conditions are added to terminate recursion in a timely manner, less recursion is performed and the pressure on the stack storage is reduced
            Mirror (root.left);
        if (root.right!= null) {
            Mirror (root.right);
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