title: Count Ways Build Street Given Constraints
signature: function count_ways_build_street_given_constraints(n)
test_code: using Printf
  
  # SOLUTION CODE
  # ============================================
  PLACEHOLDER_CODE_BODY
  
  # TESTING CODE 
  # ============================================
  function validate_solution(actual, expected)
      return actual == expected
  end
  
  function driver(n, expected)
      try
  
          if validate_solution(PLACEHOLDER_FN_NAME(n), expected)
              return "PASSED";
          end
          return "FAILED";
      catch exception_obj
          return string(Base.typename(typeof(exception_obj)).wrapper);
      end
  end
  
  function main()
      
      result = driver(20, 54608393);
      @printf("TEST-0...%s\n",result);
      
      result = driver(1, 3);
      @printf("TEST-1...%s\n",result);
      
  end
  
  main()
source_py: def count_ways_build_street_given_constraints(n):
      dp = [([0] * (n + 1)) for i in range(2)]
      dp[0][1] = 1
      dp[1][1] = 2
      for i in range(2, (n + 1)):
          dp[0][i] = (dp[0][(i - 1)] + dp[1][(i - 1)])
          dp[1][i] = ((dp[0][(i - 1)] * 2) + dp[1][(i - 1)])
      return (dp[0][n] + dp[1][n])
source_cpp: long count_ways_build_street_given_constraints(int n) {
    long dp [ 2 ] [ n + 1 ];
    dp [ 0 ] [ 1 ] = 1;
    dp [ 1 ] [ 1 ] = 2;
    for ( int i = 2;
    i <= n;
    i ++ ) {
      dp [ 0 ] [ i ] = dp [ 0 ] [ i - 1 ] + dp [ 1 ] [ i - 1 ];
      dp [ 1 ] [ i ] = dp [ 0 ] [ i - 1 ] * 2 + dp [ 1 ] [ i - 1 ];
    }
    return dp [ 0 ] [ n ] + dp [ 1 ] [ n ];
  }