Leetcode 450. Delete Node in a BST (Medium) (cpp)

Leetcode 450. Delete Node in a BST (Medium) (cpp)

Tag: Tree

Difficulty: Medium

/*450. Delete Node in a BST (Medium)Given a root node reference of a BST and a key, delete the node with the given key in the BST. Return the root node reference (possibly updated) of the BST.Basically, the deletion can be divided into two stages:Search for a node to remove.If the node is found, delete the node.Note: Time complexity should be O(height of tree).Example:root = [5,3,6,2,4,null,7]key = 35/ \3   6/ \   \2   4   7Given key to delete is 3. So we find the node with value 3 and delete it.One valid answer is [5,4,6,2,null,null,7], shown in the following BST.5/ \4   6/     \2       7Another valid answer is [5,2,6,null,4,null,7].5/ \2   6\   \4   7*//*** Definition for a binary tree node.* struct TreeNode {*     int val;*     TreeNode *left;*     TreeNode *right;*     TreeNode(int x) : val(x), left(NULL), right(NULL) {}* };*/class Solution {public:TreeNode* deleteNode(TreeNode* root, int key) {if (root == NULL) {return root;}else if (root->val > key) {root->left = deleteNode(root->left, key);}else if (root->val < key) {root->right = deleteNode(root->right, key);}else {if (root->right == NULL || root->left == NULL) {return root->left == NULL ? root->right : root->left;}else {root->val = findSmallest(root->right);root->right = deleteNode(root->right, root->val);}}return root;}private:int findSmallest(TreeNode* root) {while (root->left != NULL) {root = root->left;}return root->val;}};