Question

How to check if a matrix columns contain numbers without repetition in Scala

Answer 1

import scala.collection.mutable.HashSet

object ColumnUniqueNumbers {
  def columnsHaveUniqueNumbers(matrix: Array[Array[Int]]): Boolean = {
    if (matrix.isEmpty || matrix(0).isEmpty) return true

    val numCols = matrix(0).length
    for (j <- 0 until numCols) {
      val columnSet = new HashSet[Int]()
      for (row <- matrix) {
        if (!columnSet.add(row(j))) return false // Duplicate found
      }
    }
    true
  }

  def main(args: Array[String]): Unit = {
    val matrix1 = Array(
      Array(1, 4, 7),
      Array(2, 5, 8),
      Array(3, 6, 9)
    )

    val matrix2 = Array(
      Array(1, 4, 7),
      Array(2, 4, 8),
      Array(3, 6, 9)
    )

    println(s"Matrix 1 columns have unique numbers: ${columnsHaveUniqueNumbers(matrix1)}")
    println(s"Matrix 2 columns have unique numbers: ${columnsHaveUniqueNumbers(matrix2)}")
  }
}


 
/*
run:

Matrix 1 columns have unique numbers: true
Matrix 2 columns have unique numbers: false

*/

 

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