Longest Substring Without Repeating Characters

LeetCode 3 • Medium • Sliding Window

Find the length of the longest substring without repeating characters.
Input: s = "abcabcbb" → Output: 3 (substring "abc")

TimeO(n)each char at most 2x

SpaceO(min(n,128))char set

Window: — Set: — MaxLen: —

Window

Right (expand)

Shrink

Result

Window

—

Set

—

MaxLen

—

Speed:

Ready

Press Play. Expand right, add char to set. If duplicate, shrink from left until unique. Track max length.

⌨ Type It

Practice until you don't need to look. The green highlights are the nuances to burn into memory.

# ─── LONGEST SUBSTRING WITHOUT REPEATING (LeetCode 3) ───

# Pattern: Sliding window + set — expand right, shrink when duplicate

# Time: O(n) Space: O(min(n,128))

# 1. Init: left=0, char_set=set(), result=0

# 2. Expand: for right in range(len(s)):

# 3. Shrink while duplicate: while s[right] in char_set:

# char_set.remove(s[left]); left += 1

# 4. Add & update: char_set.add(s[right]); result = max(result, right - left + 1)

# 5. Return: return result

# Vars: left, right, char_set, result

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