Solution.java

package _226;

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 * int val;
 * TreeNode left;
 * TreeNode right;
 * TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public TreeNode invertTree(TreeNode root) {
        if (root == null || (root.left == null && root.right == null)) {
            return root;
        }

        TreeNode tmpNode = root.left;
        root.left = invertTree(root.right);
        root.right = invertTree(tmpNode);

        return root;
    }

    /**
     * 为使编译通过，根据题目要求建立此类，非解题代码。
     */
    class TreeNode {
        int val;
        TreeNode left;
        TreeNode right;

        TreeNode(int x) {
            val = x;
        }
    }
}