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  1. Practice
  2. Functional Programming
  3. Recursion
  4. Pascal's Triangle
  5. Discussions

Pascal's Triangle

  • ASRagab + 3 comments
    object Solution {

  def main(args: Array[String]) {
    val row = io.Source.stdin.getLines
        .take(1)
        .map(_.trim.toInt)
        .next()

    def triangle(row: Int): Unit = {
       def doT(row: Int, prev: List[Int]): Unit = {
          if (row == 0) return
		
          val next = prev.sliding(2, 1)
                .map(pair => pair.sum)
                .toList
            
          println (next mkString " ")
	  doT(row - 1, (0 :: next) :+ 0)
       }

    doT(row, List(1))
    }
        
    triangle(row)
  }
}

    Yeah, so I am not thrilled about this. Having to append and prepend zeros seems hacky.

    • xavier_guihot + 0 comments
      def factoriel(y: Int): Int = (1 to y).foldLeft(1)(_ * _)

var k = sc.nextInt();

(0 until k).foreach( n => {

    val rowToPrint = (0 to n).map( r => {
        factoriel(n) / (factoriel(r) * factoriel(n -r))
    }).mkString(" ")

    println(rowToPrint)
})
    • SplashAttack + 0 comments
      def pascal(input: Int): Array[Int] = {
    if(input == 1) {
        println(1)
        Array.empty
    } else {   
        val result = 1 +: pascal(input - 1).sliding(2).map(_.sum).toArray :+ 1
        println(result.mkString(" "))
        result
    }
}
    • neild799 + 0 comments
      object Solution {
    def nthRow(n: Int): List[Int] = {
        val row = List(1);
        (0 until n).foldLeft[List[Int]](row)((acc, r) => acc.head*(n-r)/(r+1)::acc);
    }

    def main(args: Array[String]) {
        (0 until scala.io.StdIn.readInt()).foreach(
                i => {
                    nthRow(i).foreach(x => print(x + " "));
                    println();
                }
            );
        }
}