CodeSignal Technical Assessment Matrix Traversal and Logic 2

Question 1

Given a matrix where each cell contains a non-negative integer, you want to find the path from top-left to bottom-right (moving only right or down) that minimizes the maximum value encountered. Which algorithm is most appropriate?

Accepted Answer

Binary search combined with BFS/DFS

Answer

Binary search on the answer combined with BFS/DFS to check feasibility efficiently solves the minimax path problem.

Question 2

In a spiral traversal of an N×N matrix, after completing one full ring (outermost layer), the next ring starts at position [1][1]. For a 5×5 matrix, how many elements are in the outermost ring?

Accepted Answer

16

Answer

The outermost ring of a 5×5 matrix has 4*(5-1) = 16 elements.

Question 3

You rotate a matrix 90 degrees clockwise by first transposing it, then reversing each row. What is the equivalent operation for a 90-degree counter-clockwise rotation?

Accepted Answer

Reverse each column, then transpose

Answer

Counter-clockwise 90° rotation is achieved by reversing each column (flipping vertically) then transposing.

Question 4

A matrix is considered 'valid' if each row and each column contains all integers from 1 to N exactly once. What is this structure called?

Accepted Answer

Latin square

Answer

A Latin square is an N×N array filled with N different symbols, each occurring exactly once in each row and column.

Question 5

When performing BFS on a matrix to find the shortest path, what data structure should store the cells to visit next?

Accepted Answer

Queue (FIFO)

Answer

BFS uses a FIFO queue to explore neighbors level by level, guaranteeing shortest path in an unweighted grid.

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Codesignal Practice Test

CodeSignal Technical Assessment Matrix Traversal and Logic 2