Invert Binary Tree

方法一：

struct TreeNode* invertTree(struct TreeNode* root) {   struct TreeNode* temp;//别忘记struct    if(root==NULL) return root;    temp=root->left;    root->left=invertTree(root->right);    root->right=invertTree(temp);    return root;}

方法二：

TreeNode* invertTree(TreeNode* root) {    if(!root) return NULL;    swap(root->left, root->right);    root->left = invertTree(root->left);    root->right = invertTree(root->right);    return root;}