FAANG · LeetCode #3

Longest Substring Without Repeating Characters — three-stage drill

1The ProblemMedium

Longest Substring Without Repeating Characters

Length of the longest substring with no repeated character.

Examples

"abcdce"→ 4"pwwkew"→ 3

2The PatternTIME O(n) · SPACE O(k)

Sliding Window

A contiguous window that grows and shrinks to stay valid.

Problems using this pattern

3The SolutionRESULT → 4

Step through it

right → 0: add "a". window "a", best = 1

Step 1 / 9

Python▎expand right · shrink left

1def lengthOfLongestSubstring(s):
2    seen = set()
3    left = best = 0
4    for right in range(len(s)):
5        while s[right] in seen:
6            seen.remove(s[left])
7            left += 1
8        seen.add(s[right])
9        best = max(best, right - left + 1)
10    return best

Arrow keys to navigate · escape to reset

All problems by pattern

Two Pointers

Sliding Window

Prefix Sum

Monotonic Deque

Shortest Subarray with Sum at Least K

Binary Search

Arrays & Hashing

Monotonic Stack

Intervals

Longest Substring Without Repeating Characters — three-stage drill

Longest Substring Without Repeating Characters

Sliding Window

Step through it

All problems by pattern

Two Pointers

Sliding Window

Prefix Sum

Monotonic Deque

Binary Search

Arrays & Hashing

Monotonic Stack

Intervals

Heap / Top-K

Backtracking

Recursive Descent