输出二叉树的镜像

TreeNode* mirrorTree(TreeNode* root) {

        if(root==NULL)

        return NULL;

        TreeNode *p=root->left;

        root->left=root->right;

        root->right=p;

        if(root->left!=NULL)

        root->left=mirrorTree(root->left);

        if(root->right!=NULL)

        root->right=mirrorTree(root->right);

        return root;

    }