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Use PracHub's coding console to write, test, and debug your solutions in Python or JavaScript. View hints, test against sample inputs, and compare with official solutions.

What difficulty level is this coding question?

This is a medium difficulty Coding & Algorithms question, commonly asked during Technical Screen rounds at Meta.

What role is this question designed for?

This question is commonly asked for Software Engineer candidates at Meta during technical interviews.

Determine feasibility and clean parentheses string

Quick Overview

This pair of problems evaluates proficiency with graph algorithms (dependency modeling and cycle detection/topological ordering) and string processing (parentheses balancing and minimal-edit transformations), focusing on algorithmic thinking, data-structure usage, and efficient linear-time solutions.

Company: Meta

Role: Software Engineer

Category: Coding & Algorithms

Difficulty: medium

Interview Round: Technical Screen

You are given two independent coding tasks. ## 1) Check if all courses/tasks can be completed You have `n` courses labeled `0..n-1` and a list of prerequisite pairs `prereq`. - Each pair `[a, b]` means: to take course `a`, you must finish course `b` first. - Return `true` if it is possible to finish all `n` courses (i.e., there is no prerequisite cycle). Otherwise return `false`. **Input** - Integer `n` - List of pairs `prereq` where each element is `[a, b]` **Output** - Boolean **Constraints (typical interview scale)** - `1 ≤ n ≤ 10^5` - `0 ≤ |prereq| ≤ 2*10^5` --- ## 2) Remove the minimum invalid parentheses Given a string `s` consisting of lowercase letters and parentheses `'('` and `')'`, remove the minimum number of parentheses so that the resulting string is **valid**. A string is valid if: - Every `')'` has a matching `'('` before it. - Parentheses are properly nested. Return **one** valid string after performing the minimum removals. **Input** - String `s` **Output** - A valid string formed by deleting the minimum number of parentheses characters **Constraints (typical interview scale)** - `1 ≤ |s| ≤ 10^5` **Notes** - Deleting letters is not allowed/needed; only delete parentheses. - If multiple answers exist, returning any one is acceptable.

Quick Answer: This pair of problems evaluates proficiency with graph algorithms (dependency modeling and cycle detection/topological ordering) and string processing (parentheses balancing and minimal-edit transformations), focusing on algorithmic thinking, data-structure usage, and efficient linear-time solutions.

Can Finish Courses

Return whether the prerequisite graph is acyclic.

Constraints

Inputs are Python literals matching the function signature.
Return a deterministic exact-match value.

Examples

Input: (2, [[1,0]])

Expected Output: True

Explanation: No cycle.

Input: (2, [[1,0],[0,1]])

Expected Output: False

Explanation: Cycle prevents completion.

Hints

Clarify edge cases before coding.
Keep the return value deterministic.

Minimum Remove To Valid Parentheses

Remove the minimum number of parentheses to make the string valid; letters are preserved.

Constraints

Inputs are Python literals matching the function signature.
Return a deterministic exact-match value.

Examples

Input: ('lee(t(c)o)de)',)

Expected Output: 'lee(t(c)o)de'

Explanation: Already valid string is unchanged.

Input: ('a)b(c)d',)

Expected Output: 'ab(c)d'

Explanation: Remove unmatched close parenthesis.

Input: ('))((',)

Expected Output: ''

Explanation: Remove all invalid parentheses.

Hints

Clarify edge cases before coding.
Keep the return value deterministic.

Quick Overview