迭代

class Solution {
public:TreeNode* insertIntoBST(TreeNode* root, int val) {if(!root) return new TreeNode(val);TreeNode*cur=root;while(cur){if(val<cur->val){if(cur->left)cur=cur->left;else{cur->left=new TreeNode(val);break;}}else if(val>cur->val){if(cur->right)cur=cur->right;else{cur->right=new TreeNode(val);break;}}}return root;}
};

递归

class Solution {
public:TreeNode* insertIntoBST(TreeNode* root, int val) {if(!root) return new TreeNode(val);else if(val>root->val) root->right=insertIntoBST(root->right,val);else root->left=insertIntoBST(root->left,val);return root;}
};

END