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Solve Triangle Rows and Top Frequencies

EricssonSoftware Engineer · Technical Screen
MediumSoftware EngineerTechnical ScreenCoding & Algorithms

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This question set evaluates understanding of combinatorial number patterns and frequency-based selection, specifically the ability to generate an additive number triangle and to identify the k most frequent elements, assessing skills in array/list manipulation, counting, and selection algorithms.

You have 1 hour to solve both coding problems.

Problem 1: Build an Additive Number Triangle

Given an integer numRows, return the first numRows rows of a triangle of numbers with the following rules:

  • Row indexing starts at 0.
  • The first and last value in every row are 1.
  • Each interior value is the sum of the two adjacent values directly above it: triangle[i][j] = triangle[i - 1][j - 1] + triangle[i - 1][j].

Return the triangle as a list of rows.

Example:

Input: numRows = 5
Output: [[1], [1,1], [1,2,1], [1,3,3,1], [1,4,6,4,1]]

Problem 2: Return the K Most Frequent Values

Given an integer array nums and an integer k, return any k distinct values that appear most frequently in nums.

If multiple values have the same frequency, any valid set of k values is acceptable. The output may be returned in any order.

Example:

Input: nums = [1,1,1,2,2,3], k = 2
Output: [1,2]

Expected approach: count frequencies and use a size-k min-heap to keep the current k most frequent values.