题目：701. 二叉搜索树中的插入操作

思路

二叉搜索树的查找规律：要插入的值val比当前节点大，往右走，比当前节点小，往左走；

代码

Method 1

class Solution {
public:void travel(TreeNode* cur, int val){if(cur == NULL){return;}if(cur->val > val){if(cur->left){travel(cur->left, val);}else // == NULL{TreeNode* temp = new TreeNode(val);cur->left = temp;}}if(cur->val < val){if(cur->right){travel(cur->right, val);}else{TreeNode* temp = new TreeNode(val);cur->right = temp;}}}TreeNode* insertIntoBST(TreeNode* root, int val) {if(root == NULL){TreeNode* temp = new TreeNode(val);root = temp;return root;}travel(root, val);return root;}
};

Method 2

class Solution {
public:TreeNode* travel(TreeNode* cur, int val){if(cur == NULL){TreeNode* node = new TreeNode(val);return node;}if(val < cur->val){cur->left = travel(cur->left, val);}if(val > cur->val){cur->right = travel(cur->right, val);}return cur;}TreeNode* insertIntoBST(TreeNode* root, int val) {root = travel(root, val);return root;}
};