Problem 181

http://projecteuler.net/index.php?section=problems&id=181

import Data.Array (range)
import Data.Array.IO (IOArray,newArray,readArray,writeArray)
import Control.Monad (forM_)
b = 60;w = 40
main = do g <- newArray ((,),(b,w))  :: IO (IOArray (Int,Int) Integer)
writeArray g (,) 1
forM_ [(i,j,k,l) | (i,j) <- tail.range $ ((,),(b,w)), (k,l) <- range((i,j),(b,w))] $ (i,j,k,l) ->
readArray g ((k-i),(l-j)) >>= t -> readArray g (k,l) >>= writeArray g (k,l).(t+)
print =<< readArray g (b,w)

多分javaのほうが可読性が高い。

public class P181{
public static void main(String[] args){
int b = 60, w = 40;
long[][] g = new long [b+1][w+1];
for(int i=;i<=b;i++)for(int j=;j<=w;j++){
if(i==&&j==) {g[][]=1;continue;}
for(int k=i;k<=b;k++)for(int l=j;l<=w;l++)g[k][l]+=g[k-i][l-j];
}
System.out.println(g[b][w]);
}
}