[LeetCode] 701. Insert into a Binary Search Tree, Medium

1. 문제

• BST와 정수 val이 주어질 때, BST가 유지되도록 val를 삽입한 뒤 반환하라.

2. 해결

/**
 * Definition for a binary tree node.
 * class TreeNode {
 *     val: number
 *     left: TreeNode | null
 *     right: TreeNode | null
 *     constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
 *         this.val = (val===undefined ? 0 : val)
 *         this.left = (left===undefined ? null : left)
 *         this.right = (right===undefined ? null : right)
 *     }
 * }
 */

function insertIntoBST(root: TreeNode | null, val: number): TreeNode | null {
    if(!root) {
        root = new TreeNode(val)
        return root;
    }
    if(!root.left && root.val > val) root.left = new TreeNode(val);
    if(!root.right && root.val < val) root.right = new TreeNode(val);

    if(root.val < val) insertIntoBST(root.right, val);
    if(root.val > val) insertIntoBST(root.left, val);
    
    return root;
};

• BST를 탐색하여, 값을 비교해 왼쪽 혹은 오른쪽에 붙인다.