0701-insert-into-a-binary-search-tree.cpp

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