Solve transaction aggregation and search tasks
Problem Description
This interview consists of three distinct coding and algorithmic tasks designed to assess your proficiency with fundamental data structures, algorithmic efficiency, and problem-solving under various constraints.
Problem 1: Transaction Balance Aggregation
Given a list of financial transactions, each containing a userId and an amount (where positive values indicate credits and negative values indicate debits), compute the final aggregated balance for each unique userId.
- Input: A list of transactions, e.g.,
[{userId: "A", amount: 100}, {userId: "B", amount: -50}, {userId: "A", amount: -20}]. - Output: A map where keys are
userIds and values are their corresponding final balances, e.g.,{"A": 80, "B": -50}. - Constraints: The solution must handle large inputs efficiently.
- Deliverables: Implement the solution and specify its time and space complexity.
Problem 2: Minimal Prefix Sum Length
Given an array of positive integers nums and a list of targets, for each target, find the minimal prefix length k such that the sum of the first k elements (sum(nums[0...k-1])) is greater than or equal to the target. If no such k exists (i.e., the total sum of nums is less than the target), return -1.
- Input: An array
nums(e.g.,[1, 2, 3, 4, 5]) and a list oftargets(e.g.,[6, 12, 1]). - Output: For each target, the minimal prefix length
k. For the example,[3, -1, 1](for target 6, sum(1,2,3)=6, k=3; for target 12, total sum is 15, but no prefix sum is exactly 12 or more; for target 1, sum(1)=1, k=1). - Constraints: Implement the solution using a prefix-sum array and binary search.
- Deliverables: Implement the solution and analyze its time and space complexity.
Problem 3: Range Sum Queries and Data Structures
Consider an immutable integer array and a scenario involving a small number of range-sum queries [L, R] (inclusive) where you need to compute the sum of elements within the specified range.
- Input: An immutable integer array (e.g.,
[1, 3, 5, 7, 9]) and queries like[0, 2](sum of1+3+5). - Deliverables:
- Write a simple recursive divide-and-conquer function to compute the sum for a given query.
- Explain when you would instead build a Segment Tree (e.g., for many queries and/or updates) and compare the trade-offs between the naive recursive approach, prefix sums, and a Segment Tree.
AI interview prep
Core dilemma
Selecting and efficiently implementing the optimal data structures and algorithms to meet specific performance requirements for aggregation and querying tasks, while understanding their inherent trade-offs across different scenarios.
3 tradeoffs and 3 stress tests locked
Interview prep
Unlock the interviewer X-Ray rubric, tradeoff matrix, stress tests, clarifying questions, and key concepts.
Solve transaction aggregation and search tasks
Problem Description
This interview consists of three distinct coding and algorithmic tasks designed to assess your proficiency with fundamental data structures, algorithmic efficiency, and problem-solving under various constraints.
Problem 1: Transaction Balance Aggregation
Given a list of financial transactions, each containing a userId and an amount (where positive values indicate credits and negative values indicate debits), compute the final aggregated balance for each unique userId.
- Input: A list of transactions, e.g.,
[{userId: "A", amount: 100}, {userId: "B", amount: -50}, {userId: "A", amount: -20}]. - Output: A map where keys are
userIds and values are their corresponding final balances, e.g.,{"A": 80, "B": -50}. - Constraints: The solution must handle large inputs efficiently.
- Deliverables: Implement the solution and specify its time and space complexity.
Problem 2: Minimal Prefix Sum Length
Given an array of positive integers nums and a list of targets, for each target, find the minimal prefix length k such that the sum of the first k elements (sum(nums[0...k-1])) is greater than or equal to the target. If no such k exists (i.e., the total sum of nums is less than the target), return -1.
- Input: An array
nums(e.g.,[1, 2, 3, 4, 5]) and a list oftargets(e.g.,[6, 12, 1]). - Output: For each target, the minimal prefix length
k. For the example,[3, -1, 1](for target 6, sum(1,2,3)=6, k=3; for target 12, total sum is 15, but no prefix sum is exactly 12 or more; for target 1, sum(1)=1, k=1). - Constraints: Implement the solution using a prefix-sum array and binary search.
- Deliverables: Implement the solution and analyze its time and space complexity.
Problem 3: Range Sum Queries and Data Structures
Consider an immutable integer array and a scenario involving a small number of range-sum queries [L, R] (inclusive) where you need to compute the sum of elements within the specified range.
- Input: An immutable integer array (e.g.,
[1, 3, 5, 7, 9]) and queries like[0, 2](sum of1+3+5). - Deliverables:
- Write a simple recursive divide-and-conquer function to compute the sum for a given query.
- Explain when you would instead build a Segment Tree (e.g., for many queries and/or updates) and compare the trade-offs between the naive recursive approach, prefix sums, and a Segment Tree.