We use cookies to ensure you have the best browsing experience on our website. Please read our cookie policy for more information about how we use cookies.
  1. Prepare
  2. Functional Programming
  3. Recursion
  4. Pascal's Triangle
  5. Discussions

Pascal's Triangle

  • mihassan
     + 2 comments

    I am using a trick where infinte series can be used to contruct the same series, similar to how fibonacci series is generated:

    fibs = 0 : 1 : zipWith (+) fibs (tail fibs)

    For pascal triangle, we start using the first row, and then use each row to calculate the next row.

    pascalTriangle = 
    [1] : map nextRow pascalTriangle
  where 
    nextRow = ([1] ++). (++ [1]). pairSum
    pairSum x = zipWith (+) x (tail x)

showPascalTriangle = 
    map listToString pascalTriangle
  where
    listToString = unwords. map show
    

main = getLine >>= putStrLn. unlines. flip take showPascalTriangle. read