title: Number Of Binary Trees For Given Preorder Sequence Length
signature: def numberOfBinaryTreesForGivenPreorderSequenceLength(n: Int) = {
test_code: import scala.collection.mutable.HashMap
  import scala.collection.immutable.HashSet
  
  
  // SOLUTION CODE
  // ============================================
  PLACEHOLDER_CODE_BODY
  
  
  // TESTING CODE 
  // ============================================
  def validateSolution(actual: Int , expected: Int): Boolean = {
      actual.toString == expected.toString
  }
  
  def driver(n: Int, expected: Int): String = {
      try {
          if (validateSolution(PLACEHOLDER_FN_NAME(n),expected)) {
              "PASSED"
          } else{
              "FAILED"
          }
      }catch{
          case e: Exception => {e.getClass.getName}
      }
  
  }
  object QuestionEvaluator extends App {
  
      println(s"TEST-0...${driver(
        15, 
        9694845    
      )}")   
  
  
      println(s"TEST-1...${driver(
        11, 
        58786    
      )}")   
  
  
      println(s"TEST-2...${driver(
        11, 
        58786    
      )}")   
  
  
      println(s"TEST-3...${driver(
        15, 
        9694845    
      )}")   
  
  }
  
source_py: def number_of_binary_trees_for_given_preorder_sequence_length(n):
      BT = ([0] * (n + 1))
      BT[0] = BT[1] = 1
      for i in range(2, (n + 1)):
          for j in range(i):
              BT[i] += (BT[j] * BT[((i - j) - 1)])
      return BT[n]
source_cpp: int number_of_binary_trees_for_given_preorder_sequence_length(int n) {
    int BT [ n + 1 ];
    memset ( BT, 0, sizeof ( BT ) );
    BT [ 0 ] = BT [ 1 ] = 1;
    for ( int i = 2;
    i <= n;
    ++ i ) for ( int j = 0;
    j < i;
    j ++ ) BT [ i ] += BT [ j ] * BT [ i - j - 1 ];
    return BT [ n ];
  }