Interview Cheat Sheets | Matrix Cheat Sheet

December 23rd, 2023

Introduction

This article will serve to further summarize the excellent overview of matrices from the tech interview handbook.

Overview

  • A matrix is a 2-dimensional array, often used in dynamic programming or graph traversal problems.
  • Matrices can represent graphs, with each cell as a node having 4 neighbors (except edge and corner cells).

Corner Cases:

  • Consider empty matrices, 1x1 matrices, and matrices with only one row or column.

Techniques:

  • Creating an empty N x M matrix is crucial for traversal or dynamic programming.

    • An example of creating an empty m x n matrix in typescript:

      function createEmptyMatrix(m: number, n: number): number[][] {
  return Array.from({ length: m }, () => Array(n).fill(0));
}

    • An example of copying an m x n matrix in typescript:

      function copyMatrix(matrix: number[][]): number[][] {
  return matrix.map((row) => [...row]);
}

  • Transposing a matrix involves interchanging its rows and columns.

    • An example of transposing an m x n matrix in typescript:

      function transposeMatrix(matrix: number[][]): number[][] {
  return matrix[0].map((_, columnIndex) =>
    matrix.map((row) => row[columnIndex])
  );
}

Essential Questions:

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