Longest Substring Without Repeating Characters

Medium 30 pts New · no attempts yet csharp

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Longest Substring Without Repeating Characters — DE Shaw interview prep · Sliding Window

Classic interview problem #3.

Input (stdin)

Line 1: string

Output (stdout)

Length of longest substring without repeats

Your program must read from stdin and write the answer to stdout (no extra debug text).

Examples

Sample

Input

abcabcbb

Output

Static hints

Input format: Line 1: string
DSA Interview 150 — Sliding Window
Problem #3
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Sliding Window

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Your solution

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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();
var seen = new Dictionary<char, int>();
int best = 0, start = 0;
for (int i = 0; i < s.Length; i++) {
    if (seen.ContainsKey(s[i]) && seen[s[i]] >= start) start = seen[s[i]] + 1;
    seen[s[i]] = i;
    best = Math.Max(best, i - start + 1);
}
Wi(best);
    }
}

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Explanation

Step 1 / 1

DE Shaw interview context: Longest Substring Without Repeating Characters 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 #3.

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