Step through the algorithm visually — use Play or the step buttons (inspired by AlgoMaster / visualgo).
HCLTech interview context: Valid Palindrome is a Easy Two Pointers problem — Shrink the search space from both ends; works on sorted arrays and palindromes.
Use the animation above to step through each move before writing code.
Pattern: Two Pointers
Read from stdin, write to stdout. Classic interview problem #125.
Valid Palindrome — HCLTech interview prep · Two Pointers
Classic interview problem #125.
Input (stdin)
Line 1: string
Output (stdout)
true or false
Your program must read from stdin and write the answer to stdout (no extra debug text).
A man, a plan, a canal: Panama
true
| 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()
{
string s = Console.ReadLine();
int l = 0, r = s.Length - 1;
bool ok = true;
while (l < r) {
while (l < r && !char.IsLetterOrDigit(s[l])) l++;
while (l < r && !char.IsLetterOrDigit(s[r])) r--;
if (char.ToLower(s[l]) != char.ToLower(s[r])) { ok = false; break; }
l++; r--;
}
Wb(ok);
}
}Try solving on your own first, then reveal the official answer.