Maximum Length Substring With Two Occurrences Python/Java solution

Most implementations use the same sliding window logic across languages. Python typically uses a dictionary or collections.Counter, while Java uses HashMap or an int array for character counts. Both maintain two pointers and update frequencies while ensuring each character appears at most twice.

How to solve Maximum Length Substring With Two Occurrences in O(n)?

Use a sliding window with two pointers and a frequency map. Expand the right pointer while counting characters. If a character appears more than twice, move the left pointer forward and decrease counts until the window becomes valid again. Track the maximum window length during the scan.

What is the best approach for Maximum Length Substring With Two Occurrences?

The sliding window with a hash map is the most efficient approach. It maintains a dynamic window while tracking character frequencies and ensures no character appears more than twice. This method runs in O(n) time because each character is processed at most twice, once when expanding the window and once when shrinking it.

Is Maximum Length Substring With Two Occurrences asked at Google/Amazon/Meta?

Substring constraint problems using sliding window patterns frequently appear in interviews at companies like Amazon, Google, and Meta. Variants include limiting distinct characters, limiting frequency, or finding longest valid substrings under specific constraints.

What data structure is used in Maximum Length Substring With Two Occurrences?

The core data structure is a hash map (or fixed-size frequency array) to store counts of characters inside the current window. This structure allows constant-time updates and checks while the sliding window expands and shrinks.

What is the time complexity of Maximum Length Substring With Two Occurrences?

The optimal sliding window solution runs in O(n) time where n is the length of the string. Each character is added to the window once and removed at most once. Space complexity is O(1) because the frequency map only stores counts for a limited set of characters.

Description Hints 1 Solution Video 7:05

3090. Maximum Length Substring With Two Occurrences

Q: Is Maximum Length Substring With Two Occurrences easy or hard?

LeetCode classifies this problem as Easy. The difficulty mainly lies in recognizing the sliding window pattern and correctly adjusting the left pointer when a character count exceeds two.

Easy77.4% acceptance2 companies

Given a string s, return the maximum length of a substring such that it contains at most two occurrences of each character.

Example 1:

Input: s = "bcbbbcba"

Output: 4

Explanation:

The following substring has a length of 4 and contains at most two occurrences of each character: "bcbbbcba".

Example 2:

Input: s = "aaaa"

Output: 2

Explanation:

The following substring has a length of 2 and contains at most two occurrences of each character: "aaaa".

Constraints:

2 <= s.length <= 100
s consists only of lowercase English letters.

Asked at 2 companies

Walmart Labs Microsoft

Topics

Hints open one at a time

Hint 1

We can try all substrings by brute-force since the constraints are very small.

7:05

Still stuck?Read 3 approaches, or watch a walkthrough.

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1class Solution:
2    def maximumLengthSubstring(self, s: str) -> int:
3        

Starter codePython 3Spaces: 4

Examples

Case 1Case 2

Input

"bcbbbcba"

Input

"aaaa"

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