Sliding Window/Longest Substring Without Repeating CharactersMedium

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Longest Substring Without Repeating Characters

Sliding Window·Medium

Given a string s, return the length of the longest substring that contains no repeated characters.

A variable-size sliding window works well here: expand the right edge while characters stay unique, and shrink from the left whenever a duplicate appears.

Examples

Input: s = "abcabcbb"

Output: 3

The longest substring without repeats is `"abc"`.

Input: s = "bbbbb"

Output: 1

The longest substring without repeats is `"b"`.

Input: s = "pwwkew"

Output: 3

The answer is `"wke"`, with length 3. Note that `"pwke"` is a subsequence, not a substring.

Constraints

0 <= s.length <= 5 * 10^4
s consists of English letters, digits, symbols, and spaces.

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Tests

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Passed32 ms

First attempt — retry to track metric movement here.

Your approach

Pattern:Sliding Window
Time:O(N)
Space:O(1)

Complete approach — pattern and complexity both named.

Coach

What you got right

You correctly matched the sorted input requirement and implemented a linear-time scan using two pointers.

Where it diverged

No divergence detected. The code correctly aligns with the stated approach.

Next attempt: focus on

Try solving related sliding window problems to build familiarity with two-pointer variants.

Signals

No signals fired — clean run, you stayed in flow.