701. Insert into a Binary Search Tree

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My Solution

The Key Idea for Solving This Coding Question

C++ 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) {}
 * };
 */

class Solution {
public:
    TreeNode *insertIntoBST(TreeNode *root, int val) {
        TreeNode *newNode = new TreeNode(val);
        if (root == nullptr) {
            return newNode;
        }

        TreeNode *node = root;
        while (node != nullptr) {
            if (node->val < val) {
                if (node->right == nullptr) {
                    node->right = newNode;
                    break;
                }
                node = node->right;
            } else {
                if (node->left == nullptr) {
                    node->left = newNode;
                    break;
                }
                node = node->left;
            }
        }

        return root;
    }
};

Time Complexity

$O(logn)$
n is the number of nodes in the BST.

Space Complexity

$O(1)$