450. 删除二叉搜索树中的节点

. - 力扣（LeetCode） 

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    TreeNode* deleteNode(TreeNode* root, int key) {
        if(!root)
            return nullptr;
        if(root->val<key){
            root->right=deleteNode(root->right, key);
            return root;
        }
        if(root->val>key){
            root->left=deleteNode(root->left, key);
            return root;
        }
        if(root->val == key){
            if(!root->left && !root->right)
                return nullptr;
            if(!root->right)
                return root->left;
            if(!root->left)
                return root->right;
            
            TreeNode* node=root->right;
            while(node->left)
                node=node->left;
            root->right = deleteNode(root->right, node->val);
            node->left=root->left;
            node->right=root->right;
            return node;

            
        }
            
        return root;
    }
};