题目：

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代码（首刷看解析）：

class Solution {
public:TreeNode* deleteNode(TreeNode* root, int key) {if(root==nullptr){return nullptr;}if(root->val > key ){root->left = deleteNode(root->left,key);return root;}if(root->val < key ){root->right = deleteNode(root->right,key);return root;}if(root->val == key){if(root->left==nullptr && root->right == nullptr){return nullptr;}if(root->left==nullptr){return root->right;}if(root->right==nullptr){return root->left;}if(root->right&&root->left){TreeNode* successor = root->right;while(successor->left){successor=successor->left;}root->right=deleteNode(root->right,successor->val);successor->right=root->right;successor->left=root->left;return successor;}}return root;}
};

代码（二刷看解析 2024年1月31日）

class Solution {
public:TreeNode* deleteNode(TreeNode* root, int key) {if (!root) return nullptr;if (root->val == key) {if (!root->left && !root->right){delete root;return nullptr;}else if (!root->left) {auto ret = root->right;delete root;return ret;} else if (!root->right) {auto ret = root->left;delete root;return ret;}else{TreeNode* cur = root->right;while (cur->left) {cur = cur->left;}cur->left = root->left;auto ret = root;root = root->right;delete ret;return root;}}if(key < root->val) root->left = deleteNode(root->left, key);if(key > root->val) root->right = deleteNode(root->right,key);return root;}
};