Step through the algorithm visually — use Play or the step buttons (inspired by AlgoMaster / visualgo).
Apple interview context: Lowest Common Ancestor of a Binary Search Tree is a Medium Trees problem — DFS (recursion/stack) or BFS (queue); clarify preorder/inorder/postorder.
Use the animation above to step through each move before writing code.
Pattern: Trees
Read from stdin, write to stdout. Classic interview problem #235.
Lowest Common Ancestor of a Binary Search Tree — Apple interview prep · Trees
Classic interview problem #235.
Input (stdin)
Line 1: level-order (-1 = null)
Output (stdout)
Tree aggregate (Lowest Common Ancestor of a Binary Search Tree)
Your program must read from stdin and write the answer to stdout (no extra debug text).
3 9 20 -1 -1 15 7
54
| Test | Status | Details |
|---|
Ready — edit the code above and click Run or Submit.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
class Program
{
static int[] Ria(string line = null)
{
line ??= Console.ReadLine();
if (string.IsNullOrWhiteSpace(line)) return Array.Empty<int>();
return line.Trim().Split(new[] { ' ', ',', '\t' }, StringSplitOptions.RemoveEmptyEntries)
.Select(int.Parse).ToArray();
}
static string[] Rsa()
{
int n = int.Parse(Console.ReadLine());
var arr = new string[n];
for (int i = 0; i < n; i++) arr[i] = Console.ReadLine();
return arr;
}
static void W(params object[] parts) => Console.WriteLine(string.Join(" ", parts));
static void Wb(bool v) => Console.WriteLine(v ? "true" : "false");
static void Wi(int v) => Console.WriteLine(v);
static void Ws(string v) => Console.WriteLine(v);
static void Main()
{
var vals = Ria();
Wi(vals.Where(x => x >= 0).Sum());
}
}Try solving on your own first, then reveal the official answer.