Coding - Count Disjoint String Pairs

[ OK ] eab4ffe3-dbf4-4c13-8439-c1773b436a84 — full content available

[ INFO ] category: Coding difficulty: unknown freq: first seen: 2026-03-13

[UNKNOWN][CODING]

$ cat problem.md

While there is no single widely documented problem titled "Count Disjoint String Pairs" specifically linked to Rippling, the company is known for asking high-impact string manipulation and array problems that focus on clean logic and testing. 1 5

Based on common Rippling interview patterns and similar competitive programming problems, the "Count Disjoint String Pairs" problem typically follows this structure:

Problem Statement

Given an array of strings, count the number of pairs (𝑖,𝑗) such that 𝑖<𝑗 and the strings 𝑠[𝑖] and 𝑠[𝑗] are disjoint. Two strings are considered disjoint if they have no common characters.

Input: An array of strings words.
Output: An integer representing the count of disjoint pairs.
Example: Input: ["abc", "de", "af"] Output: 1 (The only disjoint pair is ("abc", "de"). "abc" and "af" share 'a'; "de" and "af" share nothing, but if the list were ["abc", "de", "f"], then ("abc", "de"), ("abc", "f"), and ("de", "f") would all be disjoint).

Key Rippling Interview Characteristics

Practical Constraints: Expect to handle cases where efficiency matters. A brute-force 𝑂(𝑁2⋅𝐿) (where Lcap L𝐿 is string length) may be too slow if Ncap N𝑁 is large.
Bitmasking Strategy: A common optimization for "disjoint" problems involves representing each string as a 26-bit integer (bitmask) where the ii𝑖-th bit is set if the ii𝑖-th character of the alphabet is present.
Testing Focus: Rippling interviews often emphasize passing hidden test cases and writing modular, testable code. Reddit +2

Problem Statement

Input: An array of strings words.
Output: An integer representing the count of disjoint pairs.
Example: Input: ["abc", "de", "af"] Output: 1 (The only disjoint pair is ("abc", "de"). "abc" and "af" share 'a'; "de" and "af" share nothing, but if the list were ["abc", "de", "f"], then ("abc", "de"), ("abc", "f"), and ("de", "f") would all be disjoint).

Key Rippling Interview Characteristics

Practical Constraints: Expect to handle cases where efficiency matters. A brute-force 𝑂(𝑁2⋅𝐿) (where Lcap L𝐿 is string length) may be too slow if Ncap N𝑁 is large.
Bitmasking Strategy: A common optimization for "disjoint" problems involves representing each string as a 26-bit integer (bitmask) where the ii𝑖-th bit is set if the ii𝑖-th character of the alphabet is present.
Testing Focus: Rippling interviews often emphasize passing hidden test cases and writing modular, testable code. Reddit +2

Coding - Count Disjoint String Pairs

Problem Statement

Key Rippling Interview Characteristics

Related Problems to Practice

Coding - Count Disjoint String Pairs

Problem Statement

Key Rippling Interview Characteristics

Related Problems to Practice