面试思路：二叉树的镜像

操作给定的二叉树，将其变换为源二叉树的镜像。

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

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

    }

}
*/
public class Solution {
    public void Mirror(TreeNode root) {
        TreeNode tmp = null;
        if (root != null) {
            tmp = root.left;
            root.left = root.right;
            root.right = tmp;
            if (root.left != null)
                Mirror(root.left);
            if (root.right != null)
                Mirror(root.right);
        }    
    }
}

优化代码：

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

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

    }

}
*/
public class Solution {
    public void Mirror(TreeNode root) {
        if (root != null) {
            Mirror(root.left);
            Mirror(root.right);
            TreeNode temp = root.left;
            root.left = root.right;
            root.right = temp;
        }      
    }
}