二分搜索树

基本操作 O(logn)

1. 二分搜索树删除节点：

https://www.runoob.com/data-structures/binary-search-remove.html
方法：移动到要删除的节点，使用右子树最小元素覆盖节点，然后删除右子树最小节点
code

/**
 * 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) {}
 * };
 */
//找到key,使用右子树中最小的元素替换key,然后删除右子树中最下的元素
class Solution {
public:
    TreeNode* deleteNode(TreeNode* root, int key) {
        if(root == NULL)
            return NULL;
        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->left) return root->right;
        if(!root->right) return root->left;
        TreeNode*  minNode = root->right;
        while(minNode->left!=NULL){
            minNode = minNode->left;
        }
        root->val = minNode ->val;
        root->right = deleMin(root->right);
        return root;
    }
private: 
    TreeNode* deleMin(TreeNode* node){
        if(!node->left)return node->right;
        node->left = deleMin(node->left);
        return node;
    }
};