Invert Binary Tree

方法一：

struct TreeNode* invertTree(struct TreeNode* root) {
   struct TreeNode* temp;//別忘記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;
}