Longest Repeating Character Replacement

Medium 30 pts New · no attempts yet csharp

Topics

Company

Longest Repeating Character Replacement — PwC 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).

Examples

Sample

Input

AABABBA
1

Output

Static hints

Input format: Line 1: string\nLine 2: k
DSA Interview 150 — Sliding Window
Problem #424
Frequently asked at PwC
Sliding Window

Toolliyo Coach

Stuck? Get a nudge — not the answer

Progressive help: Nudge → Guide → Approach. Full solution stays behind the Solution tab.

Your solution

Editor is open — no login wall to practice.

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()
    {
        // Read from stdin (see problem statement for format)
        // Line 1: string\nLine 2: k

}
}

Ready — edit the code above and click Run or Submit.

Official solution

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);
    }
}

Prefer Coach (Nudge → Guide → Approach) before revealing. No forced signup.

Explanation

Step 1 / 1

PwC 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.

Prev Next All problems