226. Invert Binary Tree

Posted 2020-10-29 optor

原题链接：https://leetcode.com/problems/invert-binary-tree/description/
这是一道有历史典故的算法题目哦：

/**
 * Created by clearbug on 2018/2/26.
 */
public class Solution {

    public static void main(String[] args) {
        Solution s = new Solution();

        TreeNode root = new TreeNode(4);
        root.left = new TreeNode(2);
        root.left.left = new TreeNode(1);
        root.left.right = new TreeNode(3);
        root.right = new TreeNode(7);
        root.right.left = new TreeNode(6);
        root.right.right = new TreeNode(9);

        root = s.invertTree(root);
        System.out.println(root);
    }

    /**
     * 这道题目还是有历史典故的，下面我的实现是其递归实现版本，也就是做深度优先遍历吧，这也是官方答案的第一种。
     * 官方答案第二种就是使用一个队列来做广度优先遍历来进行处理吧，这里就不在说了！
     *
     * @param root
     * @return
     */
    public TreeNode invertTree(TreeNode root) {
        if (root == null || (root.left == null && root.right == null)) {
            return root;
        }

        TreeNode temp = root.left;
        root.left = root.right;
        root.right = temp;

        invertTree(root.left);
        invertTree(root.right);

        return root;
    }

}