Introduction

In this blog post, we'll share the most commonly asked coding interview questions at Acko. If you don't have months to study for your interviews, you can use AI tools like Chatmagic to generate solutions quickly and efficiently - helping you pass the interviews and get the job offer!

Problem #1: Fill Missing Data

DataFrame products +-------------+--------+ | Column Name | Type | +-------------+--------+ | name | object | | quantity | int | | price | int | +-------------+--------+ Write a solution to fill in the missing value as 0 in the quantity column. The result format is in the following example. Example 1: Input:+-----------------+----------+-------+ | name | quantity | price | +-----------------+----------+-------+ | Wristwatch | None | 135 | | WirelessEarbuds | None | 821 | | GolfClubs | 779 | 9319 | | Printer | 849 | 3051 | +-----------------+----------+-------+ Output: +-----------------+----------+-------+ | name | quantity | price | +-----------------+----------+-------+ | Wristwatch | 0 | 135 | | WirelessEarbuds | 0 | 821 | | GolfClubs | 779 | 9319 | | Printer | 849 | 3051 | +-----------------+----------+-------+ Explanation: The quantity for Wristwatch and WirelessEarbuds are filled by 0.

Topics: nan

Problem #2: Count All Valid Pickup and Delivery Options

Given n orders, each order consists of a pickup and a delivery service. Count all valid pickup/delivery possible sequences such that delivery(i) is always after of pickup(i). Since the answer may be too large, return it modulo 10^9 + 7. Example 1: Input: n = 1 Output: 1 Explanation: Unique order (P1, D1), Delivery 1 always is after of Pickup 1. Example 2: Input: n = 2 Output: 6 Explanation: All possible orders: (P1,P2,D1,D2), (P1,P2,D2,D1), (P1,D1,P2,D2), (P2,P1,D1,D2), (P2,P1,D2,D1) and (P2,D2,P1,D1). This is an invalid order (P1,D2,P2,D1) because Pickup 2 is after of Delivery 2. Example 3: Input: n = 3 Output: 90 Constraints: 1 <= n <= 500

Topics: Math, Dynamic Programming, Combinatorics

Problem #3: Parallel Courses III

You are given an integer n, which indicates that there are n courses labeled from 1 to n. You are also given a 2D integer array relations where relations[j] = [prevCoursej, nextCoursej] denotes that course prevCoursej has to be completed before course nextCoursej (prerequisite relationship). Furthermore, you are given a 0-indexed integer array time where time[i] denotes how many months it takes to complete the (i+1)th course. You must find the minimum number of months needed to complete all the courses following these rules: You may start taking a course at any time if the prerequisites are met. Any number of courses can be taken at the same time. Return the minimum number of months needed to complete all the courses. Note: The test cases are generated such that it is possible to complete every course (i.e., the graph is a directed acyclic graph). Example 1: Input: n = 3, relations = [[1,3],[2,3]], time = [3,2,5] Output: 8 Explanation: The figure above represents the given graph and the time required to complete each course. We start course 1 and course 2 simultaneously at month 0. Course 1 takes 3 months and course 2 takes 2 months to complete respectively. Thus, the earliest time we can start course 3 is at month 3, and the total time required is 3 + 5 = 8 months. Example 2: Input: n = 5, relations = [[1,5],[2,5],[3,5],[3,4],[4,5]], time = [1,2,3,4,5] Output: 12 Explanation: The figure above represents the given graph and the time required to complete each course. You can start courses 1, 2, and 3 at month 0. You can complete them after 1, 2, and 3 months respectively. Course 4 can be taken only after course 3 is completed, i.e., after 3 months. It is completed after 3 + 4 = 7 months. Course 5 can be taken only after courses 1, 2, 3, and 4 have been completed, i.e., after max(1,2,3,7) = 7 months. Thus, the minimum time needed to complete all the courses is 7 + 5 = 12 months. Constraints: 1 <= n <= 5 104 0 <= relations.length <= min(n (n - 1) / 2, 5 * 104) relations[j].length == 2 1 <= prevCoursej, nextCoursej <= n prevCoursej != nextCoursej All the pairs [prevCoursej, nextCoursej] are unique. time.length == n 1 <= time[i] <= 104 The given graph is a directed acyclic graph.

Topics: Array, Dynamic Programming, Graph, Topological Sort

Problem #4: Invalid Tweets

Table: Tweets +----------------+---------+ | Column Name | Type | +----------------+---------+ | tweet_id | int | | content | varchar | +----------------+---------+ tweet_id is the primary key (column with unique values) for this table. content consists of alphanumeric characters, '!', or ' ' and no other special characters. This table contains all the tweets in a social media app. Write a solution to find the IDs of the invalid tweets. The tweet is invalid if the number of characters used in the content of the tweet is strictly greater than 15. Return the result table in any order. The result format is in the following example. Example 1: Input: Tweets table: +----------+-----------------------------------+ | tweet_id | content | +----------+-----------------------------------+ | 1 | Let us Code | | 2 | More than fifteen chars are here! | +----------+-----------------------------------+ Output: +----------+ | tweet_id | +----------+ | 2 | +----------+ Explanation: Tweet 1 has length = 11. It is a valid tweet. Tweet 2 has length = 33. It is an invalid tweet.

Topics: Database