A trip, book, random code and additional non-sense

On a 24 hr train trip from Halifax to Toronto I enjoyed some reading from Clean Code: A Handbook of Agile Software Craftsmanship most interesting chapter so far is Object and Data Structures.

Some random coding here

Integer partition:


void gen(int lead,int postfix,int number,int *arr,int index,int originalNumber){
if(postfix<1)
return;
do{
int i=index;
arr[i++] = number - postfix;
arr[i] = postfix;
int j = 0;
int sum =0;
for(j=0;j<=index+1;j++){
cout << arr[j] << " ";
sum += arr[j];
}
cout << endl;
counter++;
gen(lead,postfix-1,postfix,arr,index+1,originalNumber-1);
lead++;
postfix = originalNumber - lead;

}while(lead < originalNumber);
}


which I thought is an awful implementation so I stole a python implementation as below


## {{{ http://code.activestate.com/recipes/218332/ (r1)
import sys
def partitions(n):
# base case of recursion: zero is the sum of the empty list
if n == 0:
yield []
return

# modify partitions of n-1 to form partitions of n
for p in partitions(n-1):
yield [1] + p
if p and (len(p) < 2 or p[1] > p[0]):
## print ["DEBUG: "] +  p
yield [p[0] + 1] + p[1:]
## end of http://code.activestate.com/recipes/218332/ }}}
print "Enter a number (0 to quit): "
n = int(sys.stdin.readline())
while n>0:
counter = 0
for p in partitions(n):
print p
counter = counter + 1
print "There were " + str(counter) + " unqiue partitions"
print "Enter a number (0 to quit): "
n = int(sys.stdin.readline())

the equivalent C# implementation is


public static IEnumerable<List<int>> intpart(int n)
 {
   if (n < 0)
                yield return null;
            if (n == 0)
                yield return new List<int>();
            foreach (List<int> list in intpart(n - 1))
            {
                if (list == null) break;
                var temp = new List<int>();
                temp.Add(1);
                temp.AddRange(list);
                yield return temp;

                if (list.Count > 0 && (list.Count < 2 || list[1] > list[0]))
                {
                    var newList = new List<int>();
                    newList.Add(list[0] + 1);
                    newList.AddRange(list.GetRange(1, list.Count - 1));
                    yield return newList;
                }
            }
  }


and playing with python and generating permutations


def ListPermutations(prefix,original):
    if original == "":
        print prefix
    else:
        index = 0
        length  = len(original)
        while index < length:
            if index < length-1 and original[index]==original[index+1]:
                index = index + 1
                continue
            newprefix = prefix + original[index]
            neworiginal = original[0:index]+original[index+1:]
            index = index + 1
            ListPermutations(newprefix,neworiginal)
          
##
and now java


public static void generate(int []array){
        while(array[0]
        {
            int sum = 0;
            int n = array.length;
            int stopIndex = -1;          
            for(int i:array){
                sum+= i;
                stopIndex++;              
                if(sum>=n){
                    System.out.print( ((sum-n)>0?(sum-n):i) );                  
                    break;
                }
                System.out.print(i + " ");
            }
            sum = 0;
            counter++;
            System.out.println();                                  
            int startIndex = 1;          
            for(int i=stopIndex-1;i>=startIndex;i--)
            {
                if(array[i]
                {
                    array[i]++;
                    for(int j=i+1;j
                        array[j]=1;
                    generate(array);
                   
                }
            }
            array[0]++;
            for(int i=1;i
            {
                array[i]=1;
            }
        }
    }

as for the additional non-sense, seize your moment for you may not get a second chance and enjoy http://www.youtube.com/watch?v=g9hMLnmeNm4  awfully nice sound and words