title: Painting Fence Algorithm
signature: paintingFenceAlgorithm(n, k) {
test_code: import 'dart:convert';
  
  // SOLUTION CODE
  // ============================================
  PLACEHOLDER_CODE_BODY
  
  // TESTING CODE 
  // ============================================
  bool validateSolution(int actual, int expected){
      return actual.toString() == expected.toString();
  }
  
  String driver(n, k, int expected){
      try
      {
          if (validateSolution(PLACEHOLDER_FN_NAME(n, k), expected)){
              return "PASSED";
          }
          return "FAILED";
      }catch(exception_object){
          return exception_object.runtimeType.toString();
      }
  }
  
  int main() {
  
      print("TEST-0...${driver(
          6, 30, 
          725841870)
      }");
  
      print("TEST-1...${driver(
          23, 87, 
          370622679)
      }");
  
      print("TEST-2...${driver(
          89, 31, 
          7554776)
      }");
  
      print("TEST-3...${driver(
          63, 36, 
          76740139)
      }");
  
      print("TEST-4...${driver(
          23, 68, 
          647498520)
      }");
  
      print("TEST-5...${driver(
          44, 66, 
          70208793)
      }");
  
      print("TEST-6...${driver(
          81, 18, 
          227130467)
      }");
  
      print("TEST-7...${driver(
          43, 73, 
          204618786)
      }");
  
      print("TEST-8...${driver(
          9, 42, 
          797370673)
      }");
  
      print("TEST-9...${driver(
          41, 98, 
          903959704)
      }");
  
      return 0;
  }
source_py: def painting_fence_algorithm(n, k):
      total = k
      mod = 1000000007
      (same, diff) = (0, k)
      for i in range(2, (n + 1)):
          same = diff
          diff = (total * (k - 1))
          diff = (diff % mod)
          total = ((same + diff) % mod)
      return total
source_cpp: long painting_fence_algorithm(int n, int k) {
    long total = k;
    int mod = 1000000007;
    int same = 0, diff = k;
    for ( int i = 2;
    i <= n;
    i ++ ) {
      same = diff;
      diff = total * ( k - 1 );
      diff = diff % mod;
      total = ( same + diff ) % mod;
    }
    return total;
  }