Solve sliding-window and disjoint-string-pairs tasks

Q: Solve sliding-window and disjoint-string-pairs tasks

This question evaluates proficiency in string-processing algorithms, sliding-window techniques, efficient set or bitmask representations, and combinatorial pair counting under strict time and space constraints.

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Question

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Task A (Sliding Window)

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

Input: a string s
Output: an integer (maximum length)
Constraints (assume): 1 <= len(s) <= 2e5 ; ASCII characters.

Task B (Disjoint-character string pairs)

Given a list of strings words, count the number of unique unordered pairs (i, j) with i < j such that words[i] and words[j] share no common characters.

Two strings “share no common characters” if there is no character c that appears in both strings.
Count each pair once (order doesn’t matter).

Example

Input: ["apple", "banana", "peach", "kiwi"]

Valid unique pairs include:

("apple", "kiwi")
("banana", "kiwi")
("peach", "kiwi")

Requirements

Design an algorithm with time complexity O(n log n) (or better) where n = len(words).

Input: list of strings words
Output: integer count of valid pairs
Constraints (assume): 1 <= n <= 2e5 ; each word length up to 1e3 ; characters are lowercase a – z (state any additional assumptions you need).

Solve sliding-window and disjoint-string-pairs tasks

Quick Overview

Task A (Sliding Window)

Task B (Disjoint-character string pairs)

Example

Requirements

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