title: Painting Fence Algorithm
signature: pub fn painting_fence_algorithm(n: i32, k: i32) -> i32 {
test_code: use std::collections::HashMap;
  use std::collections::HashSet;
  use std::cmp::*;
  use std::collections::*;
  use std::fmt::*; 
  
  
  // SOLUTION CODE
  // ============================================
  PLACEHOLDER_CODE_BODY
  
  // TESTING CODE 
  // ============================================
  pub fn validate_solution(actual: i32, expected: i32)->bool{
  return actual==expected
  }
  pub fn driver(n: i32, k: i32, expected: i32)->String{
      if validate_solution(PLACEHOLDER_FN_NAME(n, k), expected) {
        return "PASSED".to_string();
      };
      return "FAILED".to_string();
  
  }
  
  fn main() {
      println!("TEST-0...{}", driver(
        6, 30, 
        725841870
      ));
      
      println!("TEST-1...{}", driver(
        23, 87, 
        370622679
      ));
      
      println!("TEST-2...{}", driver(
        89, 31, 
        7554776
      ));
      
      println!("TEST-3...{}", driver(
        63, 36, 
        76740139
      ));
      
      println!("TEST-4...{}", driver(
        23, 68, 
        647498520
      ));
      
      println!("TEST-5...{}", driver(
        44, 66, 
        70208793
      ));
      
      println!("TEST-6...{}", driver(
        81, 18, 
        227130467
      ));
      
      println!("TEST-7...{}", driver(
        43, 73, 
        204618786
      ));
      
      println!("TEST-8...{}", driver(
        9, 42, 
        797370673
      ));
      
      println!("TEST-9...{}", driver(
        41, 98, 
        903959704
      ));
      
  }
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;
  }