Step through the algorithm visually — use Play or the step buttons (inspired by AlgoMaster / visualgo).
Infosys interview context: Longest Repeating Character Replacement is a Medium Sliding Window problem — Maintain a window [L, R] and update counts as you expand or contract.
Use the animation above to step through each move before writing code.
Pattern: Sliding Window
Read from stdin, write to stdout. Classic interview problem #424.
Longest Repeating Character Replacement — Infosys interview prep · Sliding Window
Classic interview problem #424.
Input (stdin)
Line 1: string\nLine 2: k
Output (stdout)
Max length after k replacements
Your program must read from stdin and write the answer to stdout (no extra debug text).
AABABBA 1
4
| 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 k = int.Parse(Console.ReadLine());
var freq = new int[26];
int start = 0, maxFreq = 0, best = 0;
for (int i = 0; i < s.Length; i++) {
maxFreq = Math.Max(maxFreq, ++freq[s[i] - 'A']);
while ((i - start + 1) - maxFreq > k) freq[s[start++] - 'A']--;
best = Math.Max(best, i - start + 1);
}
Wi(best);
}
}Try solving on your own first, then reveal the official answer.