[Haskell-cafe] C++

11 Dec 2012

      Hello All
I am trying to transform this C++ code in Haskell. In case any one
interested this is solution of SPOJ
http://www.spoj.com/problems/DIEHARD/problem.

#include<cstdio>
#include<iostream>
#include<cstring>
using namespace std;

int memo[1100][1100] ;

int recurse( int h , int a , int cnt , bool flag )
    {
      if ( h <= 0 || a <= 0 ) return cnt ;
      if ( memo[h][a] ) return memo[h][a] ;
      if ( flag ) memo[h][a] =  recurse ( h + 3 , a + 2 , cnt + 1 , !flag
)  ;
      else
         memo[h][a] = max ( memo[h][a] ,  max ( recurse ( h - 5 , a - 10 ,
cnt + 1 , !flag ) , recurse ( h - 20 , a + 5 , cnt + 1 , !flag ) ) ) ;

     return memo[h][a];
   }

int main()
  {
    int n , a , b ;
    scanf( "%d", &n );
    for(int i = 0 ; i < n ; i++)
    {
     memset ( memo , 0 , sizeof memo ) ;
     scanf("%d%d", &a , &b );
     printf("%d\n" , recurse( a , b , -1 ,  1 ));
     if( i != ( n - 1 ) ) printf("\n");
    }

  }

I am stuck with that memo[1100][1100] is global variable so I tried to
solve this problem using state monad ( Don't know if its correct approach
or not ) but it certainly does not seem correct to me. Till now I came up
with code. Could some one please tell me how to solve this kind of problem
( Generally we have a global variable either multi dimensional array or
map  and we store the best values found so far in the table ).

import qualified Data.Map.Strict as SM
import Control.Monad.State

{--
funsolve_WF :: Int -> Int -> Int -> Int
funsolve_WF h a cnt
     | h <= 0 || a <= 0 = cnt
     | otherwise = funsolve_Air h a ( cnt + 1 )

funsolve_Air :: Int -> Int -> Int -> Int
funsolve_Air h a cnt = max ( funsolve_WF ( h + 3 - 5 ) ( a + 2 - 10 ) cnt'
) ( funsolve_WF ( h + 3  - 20 )  ( a + 2  + 5 )  cnt' ) where
                      cnt' = cnt + 1
--}

funSolve :: Int -> Int -> Int -> Bool -> State ( SM.Map ( Int , Int )  Int
) Int
funSolve hl am cnt f
    | hl <= 0 && am <= 0 = return cnt
    | otherwise = do
            mp <- get
            case () of
               _| SM.member ( hl , am ) mp -> return  mp SM.! ( hl , am )
                | f -> do
                      --here I have to insert the value return by function
funSolve ( hl + 3 ) ( am + 2 ) (  cnt + 1 )  ( not f ) to map whose key is
( hl , am )
                        let k = evalState ( funSolve ( hl + 3 ) ( am + 2 )
( cnt + 1 ) ( not f ) ) mp
                        modify ( SM.insert ( hl , am ) k )

                | otherwise ->  do
                       do
                        let k_1 = evalState ( funSolve ( hl - 5 )  ( am -
10 )  ( cnt + 1 ) ( not f  ) ) mp
                            k_2 = evalState ( funSolve ( hl - 20 ) ( am +
5  )  ( cnt + 1 ) ( not f  ) ) mp
                            k_3 =  mp SM.! ( hl , am )
                        modify ( SM.insert ( hl , am )  ( maximum [ k_1 ,
k_2 , k_3 ] )  )

Regards
Mukesh Tiwari

[Haskell-cafe] C++

mukesh tiwari