Matrix2026-04-04

My Solution: Exercism Matrix solution

Instructions

Parse a matrix string (rows separated by newlines, numbers separated by spaces) and provide access to rows and columns. Rows read left-to-right, columns read top-to-bottom.

Solution

export class Matrix {
  readonly matrixData: number[][];
  
  constructor(input: string) {
    const line = input.split('\n');

    this.matrixData = line.map((line) => {
      const stringNumbers = line.trim().split(' ');
      return stringNumbers.map((s) => Number(s));
    })
  }

  get rows(): number[][] {
    return this.matrixData;
  }

  get columns(): number[][] {
    const rowCount = this.matrixData.length;
    const colCount = this.matrixData[0].length;

    const cols: number[][] = [];
    for (let j = 0; j < colCount; j++) {
      cols[j] = [];
    }

    for (let i = 0; i < rowCount; i++) {
      for (let j = 0; j < colCount; j++) {
        cols[j][i] = this.matrixData[i][j];
      }
    }

    return cols;
  }
}

Tests

// Extract row from one number matrix
const matrix1 = new Matrix('1')
console.log(matrix1.rows[0]); // [1]

// Extract row
const matrix2 = new Matrix('1 2\n3 4')
console.log(matrix2.rows[1]); // [3, 4]

// Extract column
const matrix3 = new Matrix('1 2 3\n4 5 6\n7 8 9')
console.log(matrix3.columns[2]); // [3, 6, 9]

// Extract column from non-square matrix
const matrix4 = new Matrix('1 2 3\n4 5 6\n7 8 9\n8 7 6')
console.log(matrix4.columns[2]); // [3, 6, 9, 6]

Mental Model

• split('\n'): Breaks input into rows by newline character
• map(): Transforms each row string into an array of numbers
• trim().split(' '): Removes whitespace then splits numbers by spaces
• Number(s): Converts string numbers to actual numbers
• Getter properties: get rows() and get columns() act like properties but contain logic
• Column extraction: Nested loops with cols[j][i] = this.matrixData[i][j] swap row/column indices to transpose the matrix