title: Count Distinct Occurrences As A Subsequence
signature: def countDistinctOccurrencesAsASubsequence(s: String, t: String) = {
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(s: String, t: String, expected: Int): String = {
      try {
          if (validateSolution(PLACEHOLDER_FN_NAME(s, t),expected)) {
              "PASSED"
          } else{
              "FAILED"
          }
      }catch{
          case e: Exception => {e.getClass.getName}
      }
  
  }
  object QuestionEvaluator extends App {
  
      println(s"TEST-0...${driver(
        "banana", "ban", 
        3    
      )}")   
  
  
      println(s"TEST-1...${driver(
        "49597223", "42", 
        2    
      )}")   
  
  
      println(s"TEST-2...${driver(
        "1000010000011", "010", 
        20    
      )}")   
  
  
      println(s"TEST-3...${driver(
        "BTlzufK", "EpsVuzP lf", 
        0    
      )}")   
  
  
      println(s"TEST-4...${driver(
        "3474007", "370", 
        2    
      )}")   
  
  
      println(s"TEST-5...${driver(
        "0010", "00000", 
        0    
      )}")   
  
  
      println(s"TEST-6...${driver(
        "dKHhoTD", "doT", 
        1    
      )}")   
  
  
      println(s"TEST-7...${driver(
        "9123259723", "123", 
        4    
      )}")   
  
  
      println(s"TEST-8...${driver(
        "11001000111110", "0", 
        6    
      )}")   
  
  
      println(s"TEST-9...${driver(
        "iY WJlIZ", "iI", 
        1    
      )}")   
  
  }
  
source_py: def count_distinct_occurrences_as_a_subsequence(S, T):
      m = len(T)
      n = len(S)
      if (m > n):
          return 0
      mat = [[0 for _ in range((n + 1))] for __ in range((m + 1))]
      for i in range(1, (m + 1)):
          mat[i][0] = 0
      for j in range((n + 1)):
          mat[0][j] = 1
      for i in range(1, (m + 1)):
          for j in range(1, (n + 1)):
              if (T[(i - 1)] != S[(j - 1)]):
                  mat[i][j] = mat[i][(j - 1)]
              else:
                  mat[i][j] = (mat[i][(j - 1)] + mat[(i - 1)][(j - 1)])
      return mat[m][n]
source_cpp: int count_distinct_occurrences_as_a_subsequence(string S, string T) {
    int m = T . length ( ), n = S . length ( );
    if ( m > n ) return 0;
    int mat [ m + 1 ] [ n + 1 ];
    for ( int i = 1;
    i <= m;
    i ++ ) mat [ i ] [ 0 ] = 0;
    for ( int j = 0;
    j <= n;
    j ++ ) mat [ 0 ] [ j ] = 1;
    for ( int i = 1;
    i <= m;
    i ++ ) {
      for ( int j = 1;
      j <= n;
      j ++ ) {
        if ( T [ i - 1 ] != S [ j - 1 ] ) mat [ i ] [ j ] = mat [ i ] [ j - 1 ];
        else mat [ i ] [ j ] = mat [ i ] [ j - 1 ] + mat [ i - 1 ] [ j - 1 ];
      }
    }
    return mat [ m ] [ n ];
  }