← Capital One Interview Insights

Capital One·Software Engineer·Onsite - Coding / Algorithms·Senior

Senior
May 2026

Summary

Capital One Applied Researcher interview with a coding round that had a Tetris-style grid placement problem. The environment was rough since no copy-paste was allowed in the IDE, which made writing out all the block shape logic way more painful than it needed to be.

Questions Asked (1)

Q1

Given five predefined block shapes and a sequence of incoming block types, place each block on an m by n grid at the earliest valid position (smallest row, then smallest column) without overlapping. Return the final board state.

Algorithms & Data Structures
Author's notes

The logic itself isn't that complicated once you break it down.

Create a free account to read the full note

AI HintsAI Generated

Suggested Approach

Clarify the problem constraints and assumptions, then outline a simulation algorithm that processes each block in order, scanning the grid from top-left to bottom-right to find the first valid placement. Discuss data structures for efficient overlap checking and how to handle edge cases like blocks that don't fit.

Pro tip: Explicitly state your assumptions about the block shapes (e.g., fixed orientations, no rotation) and the grid boundaries, and mention that you would confirm these with the interviewer before coding. This shows attention to detail and prevents misunderstandings.

1. Clarify requirements and constraints

Ask about the exact block shapes, whether rotations are allowed, grid dimensions, and what to do if a block cannot be placed. Confirm the definition of 'earliest valid position' (smallest row, then smallest column).

2. Design the simulation algorithm

For each incoming block, iterate through grid positions in row-major order. At each position, check if the block fits without overlapping existing blocks or exceeding grid boundaries. Place at the first valid position.

3. Optimize placement checking

Use a 2D boolean array to represent occupied cells. For each candidate position, check only the cells covered by the block shape. If the grid is large, consider using a spatial index or precomputed offsets for each shape.

4. Handle edge cases

Decide behavior when a block cannot be placed (e.g., skip it, return error, or leave board unchanged). Also consider blocks that are larger than the grid or have irregular shapes.

5. Analyze complexity and test

Discuss time complexity: O(B * m * n * S) where B is number of blocks, S is max block size. Propose testing with small grids and edge cases like full board or single-cell blocks.

Key Points to Mention

  • Row-major scanning order to ensure earliest valid position (smallest row, then smallest column).
  • Use of a 2D boolean array or bitmask to track occupied cells for O(1) overlap checks.
  • Precomputation of block shape offsets relative to an anchor point (e.g., top-left of bounding box).
  • Handling of blocks that cannot be placed: skip, error, or leave board unchanged (clarify with interviewer).
  • Time and space complexity analysis, and potential optimizations for large grids.
  • Edge cases: empty sequence, blocks larger than grid, overlapping blocks, and full board.

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.