二叉搜索树
建树
删除节点，三种情况，递归处理。左右子树都存在，两种方法，一种找到左子树最大节点，赋值后递归删除。找右子树最小同理
class Solution {
public:
TreeNode* deleteNode(TreeNode* root, int key) {
if(root==NULL)return NULL;
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->left==NULL&&root->right==NULL)return NULL;
if(root->left==NULL&&root->right!=NULL)return root->right;
if(root->left!=NULL&&root->right==NULL)return root->left;
int val = findMax(root->left);
root->val=val;
root->left = deleteNode(root->left,val);
return root;
}
int findMax(TreeNode* root)
{
if(root->right==NULL)return root->val;
return findMax(root->right);
}
};