Leetcode-450 Delete Node in a BST(删除二叉搜索树中的节点)

class Solution
{
    public:
        //if doesn't find,return NULL
        TreeNode *BinarySearchTreeNodeFindMin(TreeNode *TreeRoot)
        {
            if(TreeRoot==NULL)
            {
                return NULL;
            }
            else if(TreeRoot->left==NULL)
            {
                return TreeRoot;
            }
            else
            {
                return BinarySearchTreeNodeFindMin(TreeRoot->left);
            }
        }
        TreeNode* deleteNode(TreeNode* root, int key)
        {
            if(root == NULL)
                return NULL;

            TreeNode *TmpCell;

            if(key < root -> val)
            {
                root -> left = deleteNode(root->left,key);
            }
            else if(key > root -> val)
            {
                root -> right = deleteNode(root->right,key);
            }
            else
            {
                if(root->left && root->right)
                {
                    TmpCell = BinarySearchTreeNodeFindMin(root -> right);
                    root -> val = TmpCell -> val;
                    root -> right = deleteNode(root->right,root->val);
                }
                else
                {
                    TmpCell = root;
                    if(root->left==NULL)
                    {
                        root = root -> right;
                    }
                    else if(root->right==NULL)
                    {
                        root = root -> left;
                    }
                    free(TmpCell);
                }
            }
            return root;
        }
};