title: Painting Fence Algorithm
signature: fun paintingFenceAlgorithm(n: Int, k: Int): Int {
test_code: package main
  
  import kotlin.text.*
  import kotlin.math.*
  
  
  // SOLUTION CODE
  // ===================================
  PLACEHOLDER_CODE_BODY
  
  // TESTING CODE
  // ===================================
  fun validateSolution(actual:Int, expected:Int):Boolean{
    return actual.equals(expected)
  }
  fun driver(n: Int, k: Int, expected:Int):String {
      try{
        if (validateSolution(PLACEHOLDER_FN_NAME(n, k), expected)) {
                return "PASSED"
        }
        return "FAILED"
      } catch (e: Exception){
        return e::class.simpleName as String
      }
  
  }
  
  fun main() {
      var result: String = ""
      result = driver(6, 30, 725841870)
      println("TEST-0...${result}")
      
      result = driver(23, 87, 370622679)
      println("TEST-1...${result}")
      
      result = driver(89, 31, 7554776)
      println("TEST-2...${result}")
      
      result = driver(63, 36, 76740139)
      println("TEST-3...${result}")
      
      result = driver(23, 68, 647498520)
      println("TEST-4...${result}")
      
      result = driver(44, 66, 70208793)
      println("TEST-5...${result}")
      
      result = driver(81, 18, 227130467)
      println("TEST-6...${result}")
      
      result = driver(43, 73, 204618786)
      println("TEST-7...${result}")
      
      result = driver(9, 42, 797370673)
      println("TEST-8...${result}")
      
      result = driver(41, 98, 903959704)
      println("TEST-9...${result}")
      
          
  }
  
  main()
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;
  }