Converting golfed (200 character) Ruby Code to functionally equivalent simplified JAVA code

Question

I need a simplified (Pseudo/C++/JAVA) version of this Ruby code -

def P(a)a.min<0?0:a.max<1?1:(b=a*1;t=k=0;b.map{b[k]-=1;k+=1;t+=P(b)};t)end
def d(n,a)print n>1?((0..a[-1]).map{|i|d(n-1,a+[i])};"\n"):"#{P(a)} "end
d(ARGV[0].to_i,[ARGV[1].to_i])

For context, please visit Code golf- Pascal's pyramid and higher dimensions

Here is what I have so far, Pseudo code-

/**
*   This prints out one 'row', specified by indices in array
*   for Pascal's triangle of the given dimension
**/
void doit(int dimension, list array){
    if(dimension>1){
        for(int i=0;i<=array.lastElement();++i){
            // Recursively call function with reduced dimension and
            // extended array (count index appended)
            doit(dimension-1, array.append(i));
        }
        print a newline;
    }
    else{
        print Pascal(a);
    }
}

/**
*   This calculates a specific entry in the Pascal's triangle
**/
int Pascal(list array){
    // Pascal(...,-1,...) = 0
    if(minimum(array)<0){
        return 0;
    }
    // Pascal(0,0,...,0) = 1
    else if(maximum(array)<1){
        return 1;
    }
    // Pascal(a,b,c,...) = Pascal(a-1,b,c,...) + Pascal(a-1,b-1,c,...) + Pascal(a-1,b-1,c-1,....)
    else{
        list work_array = array.copy();
        int result = 0;

        for(int i=0;i<work_array.length;++i){
            // Decrement i'th element in array
            work_array[i] = work_array[i]-1;
            // Recursively call this function with modified array
            // and add return value to result.
            result = result + Pascal(work_array);
        }

        return result;
    }
}

void main(firstArg, secondArg){
    doit(firstArg.toInt(), new list [secondArg.toInt()]);
}

Implementation of above Pseudo Code in JAVA-

import java.util.*;
public class Pascal {

    public static void main(String[] args) {
        ArrayList<Integer> power=new ArrayList<Integer>();
        power.add(3);
        doit(4,power);

    }

    public static void doit(int dimension, ArrayList<Integer> array){
        if(dimension>1){
            for(int i=0;i<=(int) array.get(array.size() - 1);++i){
                array.add(i);
                doit(dimension-1,array);
            }
            System.out.println();
        }
        else{
            System.out.print(Pa(array));
        }
    }

    public static int Pa(ArrayList<Integer> array){
        if((int)Collections.min(array) <0){
            return 0;
        }
        else if((int)Collections.max(array) <1){
            return 1;
        }
        else{
            ArrayList<Integer> work_array = new ArrayList<Integer>();
            //Collections.copy(work_array, array);
            for(int i=0;i<array.size();i++){
                work_array.set(i, array.get(i));
            }
            int result=0;
            for(int i=0;i<work_array.size();++i){
                work_array.set(i, work_array.get(i)-1);
                result=result+Pa(work_array);
            }
            return result;
        }
    }

}

But this does not give the same output, it shows an error-

Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 0, Size: 0   at java.util.ArrayList.rangeCheck(Unknown Source)   at java.util.ArrayList.set(Unknown Source)  at Pascal.Pa(Pascal.java:35)    at Pascal.doit(Pascal.java:20)  at Pascal.doit(Pascal.java:15)  at Pascal.main(Pascal.java:7)

What am I doing wrong?

Answer 1

You don't have any elements in your ArrayList<Integer> work_array = new ArrayList<Integer>(); therefore your index ist out of range, since the size() returns 0.