701.InsertIntoBST.cs

// 701. Insert into a Binary Search Tree

// You are given the root node of a binary search tree (BST) and a value to insert into the tree. Return the root node of the BST after the insertion. It is guaranteed that the new value does not exist in the original BST.

// Notice that there may exist multiple valid ways for the insertion, as long as the tree remains a BST after insertion. You can return any of them.
// Example 1:
// Input: root = [4,2,7,1,3], val = 5
// Output: [4,2,7,1,3,5]
// Explanation: Another accepted tree is:

// Example 2:
// Input: root = [40,20,60,10,30,50,70], val = 25
// Output: [40,20,60,10,30,50,70,null,null,25]
// Example 3:

// Input: root = [4,2,7,1,3,null,null,null,null,null,null], val = 5
// Output: [4,2,7,1,3,5]
/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left;
 *     public TreeNode right;
 *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
public class Solution {
    public TreeNode InsertIntoBST(TreeNode root, int val) {
        if(root == null)
            return new TreeNode(val);
        if(root.val > val)
            root.left = InsertIntoBST(root.left, val);
        else 
            root.right = InsertIntoBST(root.right, val);
        return root;
    }
}