title: Number Subsequences Ab String Repeated K Times
signature: function numberSubsequencesAbStringRepeatedKTimes($s, $k) {
test_code: <?php
  
  
  // SOLUTION CODE 
  // ============================================
  PLACEHOLDER_CODE_BODY
  
  // TESTING CODE 
  // ============================================
  function validateSolution($actual, $expected){
      return abs($actual - $expected) < 1e-06;
  }
  
  function driver($s, $k, $expected){
      try{
        if (validateSolution(PLACEHOLDER_FN_NAME($s, $k), $expected)){
          return "PASSED";
        }
        return "FAILED";
      }
      catch (Exception $exception_obj) {
        return get_class($exception_obj);
      }
  }
  
  function main(){
      printf("TEST-0...%s\n",driver(
        "abbc", 96, 
        9312.0));
      
      printf("TEST-1...%s\n",driver(
        "abahk", 7, 
        49.0));
      
      printf("TEST-2...%s\n",driver(
        "hugbabab", 5, 
        75.0));
      
      printf("TEST-3...%s\n",driver(
        "abadbc", 60, 
        7260.0));
      
      printf("TEST-4...%s\n",driver(
        "nkg9", 8, 
        0.0));
      
      printf("TEST-5...%s\n",driver(
        "jh7dab", 41, 
        861.0));
      
      printf("TEST-6...%s\n",driver(
        "abd", 87, 
        3828.0));
      
      printf("TEST-7...%s\n",driver(
        "aabb8yk", 4, 
        40.0));
      
      printf("TEST-8...%s\n",driver(
        "1111", 18, 
        0.0));
      
      printf("TEST-9...%s\n",driver(
        "PFXAhr", 8, 
        0.0));
      
  }
  
  main();
  ?>
source_py: def number_subsequences_ab_string_repeated_k_times(s, K):
      n = len(s)
      c1 = 0
      c2 = 0
      C = 0
      for i in range(n):
          if (s[i] == 'a'):
              c1 += 1
          if (s[i] == 'b'):
              c2 += 1
              C += c1
      return ((C * K) + ((((K * (K - 1)) / 2) * c1) * c2))
source_cpp: int number_subsequences_ab_string_repeated_k_times(string s, int K) {
    int n = s . length ( );
    int C, c1 = 0, c2 = 0;
    for ( int i = 0;
    i < n;
    i ++ ) {
      if ( s [ i ] == 'a' ) c1 ++;
      if ( s [ i ] == 'b' ) {
        c2 ++;
        C += c1;
      }
    }
    return C * K + ( K * ( K - 1 ) / 2 ) * c1 * c2;
  }