Appended Numbers Game

Question

Appended Numbers Game

Write a function/program that takes 2 integer parameters integer parameters or integer variables, a start number, and a max iterations count. The code should perform the following game example to construct a new number, and repeat until the number is a single digit left. eg.

3 7 2 = (3 + 7) & (7 + 2) = 10 9
1 0 9 = (1 + 0) & (0 + 9) = 1 9
1 9 = (1 + 9) = 10
1 0 = (1 + 0) = 1

Basically, taking each individual digit and adding it to its neighbour, then appending the result of the next addition as well.

Max iteration count is to safeguard infinite loops, and when the max is hit, code should dump the last 5 number steps. The same output should occur when finishing by reaching a single digit. If less than 5 steps occurred, only output the valid numbers.

Output should appear like (Step: Number) including the last 5 steps of the finished or terminated steps:

func(3541, 50) would produce this exact output format:

6: 1411
7: 552
8: 107
9: 17
10: 8

func(3541, 5) would produce:

1: 895
2: 1714
3: 885
4: 1613
5: 774

The entire calculation being:

1: 895
2: 1714
3: 885
4: 1613
5: 774
6: 1411
7: 552
8: 107
9: 17
10: 8

If there are less than 5 steps, just print those steps taken.

Only use built-in libs, parameters can be from anywhere (whatever's easiest for your language of choice). No limit on maximum integer size, and if there are overflows, let it crash.

Given this isn't too difficult from a puzzle point of view, I will give until Sunday 25th, 8PM (UTC+8) for submissions to be considered for the accepted answer, at which point the shortest of any language will be the winner.

EDIT:

Congratulations to Howard, winning with a 48 GolfScript answer.

Special mention to 2nd place marinus with a 66 APL answer.

My personal favourite (being biased towards JavaScript) was core1024's answer.

Answer 1

APL (66)

{↑¯5↑{(⍕⍵),': ',⍺}/∆,⍪⍳⍴∆←⍺{(1<⍴⍵)∧⍺>0:∆,(⍺-1)∇⊃∆←,/⍕¨2+/⍎¨⍵⋄⍬}⍕⍵}

The left argument is the maximum iteration count and the right argument is the start number.

Explanation:

• ∆←⍺{...}⍕⍵: pass the left argument as a number and the right argument as a string to the function that calculates the list of numbers, and store it in ∆:
  • (1<⍴⍵)∧⍺>0:: if the amount of digits is more than 1 and the amount of iterations left is more than 0:
    • ⍎¨⍵: evaluate each digit
    • 2+/: sum each pair
    • ⍕¨: format each number as a string
    • ∆←,/: concatenate the strings and store in ∆
    • ∆,(⍺-1)∇⊃∆: return ∆, followed by the result of applying this function to ∆ with one less iteration allowed
  • ⋄⍬: if not, return the empty list
• ∆,⍪⍳⍴∆: pair each element of ∆ with its index in ∆
• {...}/: for each pair:
  • (⍕⍵),': ',⍺: return a string with the index, followed by :, followed by the number
• ↑¯5↑: turn the list of strings into a matrix so they display on separate lines, and take the last 5 items

Test:

      5{↑¯5↑{(⍕⍵),': ',⍺}/∆,⍪⍳⍴∆←⍺{(1<⍴⍵)∧⍺>0:∆,(⍺-1)∇⊃∆←,/⍕¨2+/⍎¨⍵⋄⍬}⍕⍵}3541
1: 895 
2: 1714
3: 885 
4: 1613
5: 774 
      50{↑¯5↑{(⍕⍵),': ',⍺}/∆,⍪⍳⍴∆←⍺{(1<⍴⍵)∧⍺>0:∆,(⍺-1)∇⊃∆←,/⍕¨2+/⍎¨⍵⋄⍬}⍕⍵}3541
6: 1411
7: 552 
8: 107 
9: 17  
10: 8  

Answer 2

Mathematica, 172 characters

This is way too long, thanks to Mathematica's function names and ugly string handling (the actual "game" is only 76 of those characters), but here it is anyway:

""<>ToString/@(f=Flatten)@Take[Thread@{r=Range@Length[s=Rest@Cases[NestList[FromDigits[f@(d=IntegerDigits)[Tr/@Partition[d@#,2,1]]]&,n,m],i_/;i>0]],": "&/@r,s,"\n"&/@r},-5]

It expects the input number in variable n and the maximum number of iterations in m.

With less golf:

"" <> ToString /@
  (f = Flatten)@
   Take[
    Thread@{
      r = Range@Length[
         s = Rest@Cases[
            NestList[                 
             FromDigits[
               f@(d = IntegerDigits)[Tr /@ Partition[d@#, 2, 1]]] &,
             n,
             m
             ],
            i_ /; i > 0
            ]
         ],
      ": " & /@ r,
      s,
      "\n" & /@ r
      },
    -5
    ]

Answer 3

Ruby, 106 characters

f=->n,m{s=0
$*<<"#{s}: #{n=n.to_s.gsub(/.\B/){eval$&+?++$'[0]}.chop}"until n.to_i<10||m<s+=1
puts$*.pop 5}

I'm not 100% clear on the input rules, but if I can take n as a string I can save 5 characters, and if I can use predefined variables and write a program instead of a function, I can save another 9.

Creates a function f which can be called as follows:

f[3541, 6]

2: 1714
3: 885
4: 1613
5: 774
6: 1411

f[372, 50]

1: 109
2: 19
3: 10
4: 1

f[9999, 10]

6: 99999999999
7: 18181818181818181818
8: 9999999999999999999
9: 181818181818181818181818181818181818
10: 99999999999999999999999999999999999

Answer 4

GolfScript, 48 46 characters

{.`n*[~]n\{:s++s}*;~}*].,,\]zip{': '*}%1>-5>n*

Thank you to Peter Taylor for a two-character improvement.

Expects both numbers on the stack. Try online.

Examples:

> 4 50

> 141 50
1: 55
2: 10
3: 1

> 3541 50
6: 1411
7: 552
8: 107
9: 17
10: 8

> 3541 5
1: 895
2: 1714
3: 885
4: 1613
5: 774

Answer 5

J - 96 92 char

I'd first solved this assuming that all games terminated, and this came back to bite me in the ass during testing. Left argument is the number of steps, right argument is the starting position, which can be given as a number or a string.

([(-@(<.5<.#){.])(#\(,': '&,)&":"0,)@}.@({.~,i.0:)@:".@(<@>:@[(' '-.~[:,@":2+/\"."0@]^:)":))

This is a little too golfed and convoluted to degolf satisfyingly, so I'll say this:

• (<@>:@[(' '-.~[:,@":2+/\"."0@]^:)":) This part runs the game for the specified number of steps. 2+/\ is responsible for adding each pair of digits, and <@>:@[ in tandem with ^: controls capturing the intermediate steps of the game.
• (#\(,': '&,)&":"0,)@}.@({.~,i.0:)@:". This part formats all the results as step: result. ({.~,i.0:) is making sure we don't take too many steps, #\ is the step numbers, and the (,': '&,)&":"0 bit adds the colon and space.
• (-@(<.5<.#){.]) This portion cuts the relevant five-or-less steps out of the full list. <. means 'minimum of'.

It works, but if you start with a large enough number, the game's results quickly start growing in size, which makes J switch from integers to the imprecise doubles. Here are some examples:

   f =: ([(-@(<.5<.#){.])(#\(,': '&,)&":"0,)@}.@({.~,i.0:)@:".@(<@>:@[(' '-.~[:,@":2+/\"."0@]^:)":))
   5 f 3541
1: 895
2: 1714
3: 885
4: 1613
5: 774
   50 f 3541
6: 1411
7: 552
8: 107
9: 17
10: 8
   100 f 372
1: 109
2: 19
3: 10
4: 1

Answer 6

Javascript 139 144 150

function f(a,n){for(r=[a+=''];n--&&a[1];r.push(a=t))for(t='',i=0;a[++i];)t+=a[i-1]- -a[i];for(i=0;r[++i];)r[i+5]||console.log(i+': '+r[i])}

Ungolfed

function f(a,n)
{
  for (r=[a+='']; n-- && a[1]; r.push(a=t))
  {
    for (t = '', i = 0; a[++i]; )
    {
      t += a[i-1]- -a[i]; /* -char force conversion to number */
    }
  }   
  for (i = 0; r[++i];) r[i+5]||console.log(i+': '+r[i])
}

Answer 7

Perl, 86 84

With newlines for readability:

$s+=$_=<>;
print+(map$s=~s/.(?=(.|))/~$1?$&+$1:''/eg>1?"$_: $s$/":(),/ /..$')[-5..-1]

+ Edit: No excuse for not using -n command line switch, and then score is 82=81+1:

$s+=$_;
print+(map$s=~s/.(?=(.|))/~$1?$&+$1:''/eg>1?"$_: $s$/":(),/ /..$')[-5..-1]

And, possible integer overflow being OK, it's 81=80+1

$.=$_;
print+(map$.=~s/.(?=(.|))/~$1?$&+$1:''/eg>1?"$_: $.$/":(),/ /..$')[-5..-1]

Answer 8

Javascript, 247 278 288 307 Characters

 var t=[],q=1;function f(a,c){var x=a.toString().split(''),r='',p=parseInt;for(y in x){var i=p(y);if(i){r+=(p(x[i])+p(x[i-1])).toString();}}if(c!=0&&a>10){t.push(q+++':'+r+'\n');if(q>6){t.shift()}f(r,c-1);}console.log(t.join(',').replace(/,/g,''))}

Formatted

var t = [],
q = 1;

function f(a, c) {
 var x = a.toString().split(''),
    r = '',
    p = parseInt;
 for (y in x) {
    var i = p(y);
    if (i) {
        r += (p(x[i]) + p(x[i - 1])).toString();
    }
 }
 if (c != 0 && a > 10) {
    t.push(q+++':' + r + '\n');
    if (q > 6) {
        t.shift()
    }
    f(r, c - 1);
 }
 console.log(t.join(',').replace(/,/g, ''))
}

Edit 1: Removed ternary

Edit 2: Flipped logic for "skipping" 0 index

Edit 3: Reworked recursive calling.

Fiddle

Answer 9

Bash + coreutils, 115 bytes

for((a=$1;++i<=$2&a>9;)){
a=`paste -d+ <(fold -1<<<${a%?}) <(fold -1<<<${a#?})|bc|tr -d '
'`
echo $i: $a
}|tail -n5

Output:

$ ./appended-number.sh 3541 50
6: 1411
7: 552
8: 107
9: 17
10: 8
$ ./appended-number.sh 3541 5
1: 895
2: 1714
3: 885
4: 1613
5: 774
$ 

Answer 10

JavaScript (ECMAScript 6 Draft) - 134 Characters

f=(x,y,i=0,j=[])=>([m=''].map.call(m+x,(z,p,n)=>m+=p?+z+1*n[p-1]:m),j[i++]=i+': '+m,m.length>1&&i<y?f(m,y,i,j):j.slice(-5).join('\n'))

Examples:

f(372,5)
"1: 109
2: 19
3: 10
4: 1"

f(3541,50)
"6: 1411
7: 552
8: 107
9: 17
10: 8"

f(3541,5)
"1: 895
2: 1714
3: 885
4: 1613
5: 774"

Answer 11

Husk, 32 bytes

↑_5Ṡz+(mo`+": "sŀ)mṁs↑htU¡oṁdẊ+d

Try it online!

Output format was cumbersome, but I had to answer this in Husk.

Explanation

↑_5Ṡz+(mo`+": "sŀ)mṁs↑htU¡oṁdẊ+d
                               d convert first input to digits
                         ¡       and iterate:
                             Ẋ+  sum overlapping pairs
                           ṁd    convert to digits and flatten
                        U        truncate till fixed point
                      ht         remove first and last element
                     ↑           take second input number of values from that
                  mṁs            convert all the arrays to strings
   Ṡz+(          )               zip and concat that with:
                ŀ                range 1..length(seq)
       mo`+": "s                 convert each to string, append a colon
↑_5                              take the last 5 elements

Answer 12

Javascript, 182 bytes

function f(I,T){s=[],x=1;for(;;){d=(""+I).split("");l=d.length;if(l==1||x>T)break;for(I="",i=1;i<l;)I+=+d[i-1]+ +d[i++];s.push(x+++": "+I)}s=s.slice(-5);for(i in s)console.log(s[i])}

Answer 13

Perl, 166 147 138 129 bytes

<>=~/ /;for$i(1..$'){@n=split'',$s||$`;$s=join'',map{$n[$_]+$n[$_+1]}0..@n-2;@o=(@o,"$i: $s");$s<10&&last}print join$/,@o[-5..-1]

Ungolfed:

<> =~ / /;
for $i (1..$') {
    @n = split'', $s||$`;
    $s = join'',map {$n[$_]+$n[$_+1]} 0..@n-2;
    @o = (@o, "$i: $s");
    $s<10 && last
}
print join$/,@o[-5..-1]

I hope it's alright that it prints some extra empty lines if the whole thing takes less than 5 steps.

Answer 14

Java     524  405 365 chars [414 bytes]

Golfed version: class A{static int n=0;List<String> s=new ArrayList<>();void c(int b,int r){String d=b+"";if(r==0||b <= 9){int m=s.size();for(int i= m>=5?m-5:0;i<m;i++)System.out.println(s.get(i));return;}String l="";for(int i=0;i<d.length()-1;i++)l+=d.charAt(i)+d.charAt(i+1)-96;s.add(++n+":"+l);c(Integer.valueOf(l),--r);}public static void main(String[] a){new A().c(3541,50);}}

Readable version:

class AddDigits {
static int n = 0;
List<String> steps = new ArrayList<>();

void count(int num, int count) {
    String digits = num + "";
    if (count == 0 || num <= 9) {
        int stepsSize = steps.size();
        for (int i = stepsSize >= 5 ? stepsSize - 5 : 0; i < stepsSize; i++) {
            System.out.println(steps.get(i));
        }
        return;
    }
    String line = "";
    for (int i = 0; i < digits.length() - 1; i++) {
        line += digits.charAt(i) + digits.charAt(i + 1) - 96;
    }
    steps.add(++n + ":" + line);
    count(Integer.valueOf(line), --count);
}

public static void main(String[] args) {
    new AddDigits().count(3541, 50);
}
}

Answer 15

JavaScript 133 bytes

function f(n,g){for(c=r=[];g--;(n=s)&&(r[c++]=c+': '+s))for(i=s='',n+=s;n[++i];s+=n[i]-+-n[i-1]);console.log(r.slice(-5).join('\n'))}

Ungolfed:

function sums(num, guard) {
    for(count = res = [];guard--;(num = sum) && (res[count++] = count + ': ' + sum))
        for(i = sum = '',num += sum;num[++i];sum += num[i] -+- num[i-1]);
    console.log(res.slice(-5).join('\n'))
}

Answer 16

Java, 341 chars 371 chars

 class a{public static void main(String[] a){p(3541,50);}static void p(int n,int k){Queue<String>q=new LinkedList();int c=0;while(n>9&&c<k){c++;String r="";String p=""+n;for(int i=0;i<p.length()-1;i++)r+=((p.charAt(i)+p.charAt(i+1)-96));n=Integer.parseInt(r);q.add(c+": "+n);if(q.size()>5)q.remove();}for(String s:q){System.out.println(s);}}}

Formatted:

class a {
public static void main(String[] a) {
    p(3541, 50);
}

static void p(int n, int k) {
    Queue<String> q = new LinkedList();
    int c = 0;
    while (n > 9 && c < k) {
        c++;
        String r = "";
        String p = "" + n;
        for (int i = 0; i < p.length() - 1; i++)
            r += ((p.charAt(i) + p.charAt(i + 1) - 96));
        n = Integer.parseInt(r);
        q.add(c + ": " + n);
        if (q.size() > 5)
            q.remove();
    }
    for (String s : q) {
        System.out.println(s);
    }
}}

Thanks to user902383 i was able to reduce the code by 30 chars, by not splitting the String into an Array an using -96 instead of "Integer.valueOf()

Answer 17

Dart, 602 588 bytes

Dart is probably one of the worst languages to do this in... I'll need to find a better way to do this.

Anyway, Here's my entry:

Input through console

var steps={};void main(a){c(a[0],int.parse(a[1]));}void c(inp,m){int i=0;int n=int.parse(inp);while(++i<=m){n=addUp(n.toString());steps[i]=n;if(n<10)break;}printSteps();}int addUp(n){var ns=[];for(int i=0;i<n.length;i++){try{ns.add(n[i]+n[i+1]);}catch(e){}}return addNumbers(ns);}int addNumbers(ns){var it=ns.iterator;var s="";while(it.moveNext()){int i=0;for(var t in it.current.split('')){i+=int.parse(t);}s=s+i.toString();}return int.parse(s);}void printSteps(){int l=steps.length;for(int i=getStart(l);i<=l;i++){print("${i}:\t${steps[i]}");}}int getStart(l){int m=l-4;return m>0?m:1;}

And the ungolfed, slightly unminified version:

var steps = {};

void main(a)
{
    c(a[0], int.parse(a[1]));
}

void c(String input, int max)
{
    int i = 0;
    int n = int.parse(input);

    while(++i <= max)
    {
        n = addUp(n.toString());

        steps[i] = n;

        if(n < 10)
            break;
    }

    printSteps();
}

int addUp(String n)
{
    List numbers = [];

    for(int i = 0; i < n.length; i++)
    {
        try
        {
            numbers.add(n[i] + n[i + 1]);
        }
        catch(e){}
    }

    return addNumbers(numbers);
}

int addNumbers(List numbers)
{
    Iterator it = numbers.iterator;

    String s = "";

    while(it.moveNext())
    {
        int i = 0;
        for(String s in it.current.split(''))
        {
            i += int.parse(s);
        }

        s = s + i.toString();
    }

    return int.parse(s);
}

void printSteps()
{
    int l = steps.length;

    for(int i = getStart(l); i <= l; i++)
    {        
        print("${i}:\t${steps[i]}");
    } 
}

int getStart(int l)
{
    int m = l - 4;
    return m > 0 ? m : 1;
}

Answer 18

PERL 135 129/125 125/121 bytes

It has the same bug as Tal's answer

sub c{($e,$l)=@_;print join"\n",(grep/\d$/,map{$s="";{$e=~/(.)(.)/;redo if""ne($e=$2.$')and$s.=$1+$2};++$c.": ".($e=$s)}1..$l)[-5..-1]}

Edit 129 bytes as a function:

sub c{($e,$l)=@_;print join$/,(grep/\d$/,map{$s="";{$e=~/(.)(.)/;redo if""ne($e=$2.$')and$s.=$1+$2}"$_: ".($e=$s)}1..$l)[-5..-1]}

125 bytes as a function:

sub c{($e,$l)=@_;print+(grep/\d$/,map{$s="";{$e=~/(.)(.)/;redo if""ne($e=$2.$')and$s.=$1+$2}"$_: ".($e=$s).$/}1..$l)[-5..-1]}

125 bytes as a console script (without the hashbang):

($e,$l)=@ARGV;print join$/,(grep/\d$/,map{$s="";{$e=~/(.)(.)/;redo if""ne($e=$2.$')and$s.=$1+$2}"$_: ".($e=$s)}1..$l)[-5..-1]

121 bytes as a console script (without the hashbang):

($e,$l)=@ARGV;print+(grep/\d$/,map{$s="";{$e=~/(.)(.)/;redo if""ne($e=$2.$')and$s.=$1+$2}"$_: ".($e=$s).$/}1..$l)[-5..-1]

Expanded:

sub c
{
    ($e, $l) = @_;
    print +(grep /\d$/, map {
        $s="";
        {
            $e =~ /(.)(.)/;
            redo if "" ne ($e = $2.$') and $s .= $1 + $2
        }
        "$_: ".($e = $s).$/
    } 1 .. $l)[-5 .. -1]
}

Test with c(372,4);:

[blank line]
1: 109
2: 19
3: 10
4: 1

Test with c(3541,50);:

6: 1411
7: 552
8: 107
9: 17
10: 8

Answer 19

C# - 269

void F(int x,int y){var o=new List<string>();var i=x+"";for(int n=1;n<y&&i.Length>1;n++){var s="";for(int z=0;z<i.Length;z++){int a=i[z]-'0';var t=a+(z+1!=i.Length?i[z+1]-'0':-a);if(t!=0)s+=t;}i=s;o.Add(n+": "+i);}foreach(var p in o.Skip(o.Count-5))Debug.WriteLine(p);}

Readable:

void F(int x,int y){
    var o=new List<string>();
    var i=x+"";
    for(int n=1;n<y&&i.Length>1;n++)
    {
        var s="";
        for(int z=0;z<i.Length;z++){
            int a=i[z]-'0';
            var t=a+(z+1!=i.Length?i[z+1]-'0':-a);
            if(t!=0)
                s+=t;
        }
        i=s;
        o.Add(n+": "+i);
    }
    //Output
    foreach(var p in o.Skip(o.Count-5))
        Debug.WriteLine(p);
}

Usage:

F(3541, 50)

Output:

6: 1411
7: 552
8: 107
9: 17
10: 8

Answer 20

Cobra - 363

A rather depressing result... but hey, I still beat Java.

It should be immune to integer overflows for practical test cases.

class P
    cue init(a,b)
        base.init
        l=[]
        c=.p(a.toString)
        for x in b
            l.add("")
            y=l.count
            for i in c.count-1,l[y-1]+=(c[i]+c[i+1]).toString
            if l.last.length<2,break
            c=.p(l.last)
        z=if(y>5,y-5,0)
        for x in l[z:y],print"[z+=1]:",x
    def p(n) as List<of int>
        c=List<of int>()
        for i in n,c.add(int.parse(i.toString))
        return c

Answer 21

Python 2.7, 174 173 158 characters

Using a lot of strings to do the task.

x,n=raw_input().split()
o,i=[],0
while int(n)>i<o>9<x:x="".join(`sum(map(int,x[j:j+2]))`for j in range(len(x)-1));i+=1;o+=[`i`+": "+x]
print"\n".join(o[-5:])

Python 2.7, 155 characters

Version defining a function

def a(x,n):
 o,i,x=[],0,`x`
 while n>i<o>9<int(x):x="".join(`sum(map(int,x[j:j+2]))`for j in range(len(x)-1));i+=1;o+=[`i`+": "+x]
 print"\n".join(o[-5:])

Slightly ungolfed version:

x,n=map(int,raw_input().split())
o,i=[],1
while i<=n and x>9:
  x=int("".join(`sum(map(int,`x`[j:j+2]))` for j in range(len(`x`)-1)))
  o.append("%d: %d"%(i,x))
  i+=1
print "\n".join(o[-5:])

Answer 22

Haskell, 154

s=show
z=zipWith
m#n=concat.z(\a b->s a++": "++b++"\n")[1..].(\x->drop(length x-n)x).takeWhile(/="").iterate((\x->z(+)x(tail x)>>=s).map(\x->read[x]))$s m

example usage:

λ> 3541#5
"1: 1411\n2: 552\n3: 107\n4: 17\n5: 8\n"

To make it more readable, use putStr:

λ> putStr $ 3541#5
1: 1411
2: 552
3: 107
4: 17
5: 8

Answer 23

Groovy - 191 182 chars

Based on Thomas Rüping's solution, ported to Groovy 2.2.1:

f={it as int};n=args[0];s=f args[1];q=[];x=0;while(f(n)>9&&x<s){x++;d=n.split("");n="";for(i in 1..d.length-2)n+=f(d[i])+f(d[i+1]);q << "$x: $n"};q[-1..5].reverse().each{println it}

Execution and output:

bash$ groovy Numbers.groovy 3541 50 
6: 1411
7: 552
8: 107
9: 17
10: 8

Ungolfed:

f = {it as int}
n = args[0]
s = f args[1]

queue = []
stepCounter = 0

while (f(n) > 9 && stepCounter < s) {
    stepCounter++
    digits=n.split("")
    n=""
    for(i in 1..digits.length-2) {
        n += f(digits[i]) + f(digits[i+1])
    }
    queue << "$stepCounter: $n"
}

queue[-1..5].reverse().each{ println it }

Answer 24

**C 186 179174 **

f(int a,int z){for(int c,d,i,j=0,m[5];m[j++%5]=a,j<=z&&a/10;a=c)for(c=0,i=1;a/10;d=a%10+(a/=10)%10,c+=d*i,i*=d<10?10:100);for(i=j<5?0:j-5;i<j;printf("%d: %d\n",i,m[i++%5]));}

Slightly less golfed (mini-golfed?)

f(int a, int z)
{


for(int c,d,i,j=0,m[5];m[j++%5]=a,j<=z&&a/10;a=c)
    for(c=0,i=1;a/10;d=a%10+(a/=10)%10,c+=d*i,i*=d<10?10:100);

    for(i=j<5?0:j-5;i<j;printf("%d: %d\n",i,m[i++%5]));

}

Just allocate enough memory to store five results cyclically. The outer loop keeps going until we hit the limit or reach a single digit. The inner loop adds the last digit of the number to last digit of 1/10 of the number and adds this, multiplied by the relevant power of 10 to the result. Divide the number you first though of by 10 and repeat to get the total. Then print out up to the last five results.

Next challenge is to see if I can shave off enough to beat some scripting languages at golf.

Edit: Now compiles with warning but five characters shaved off by removing "void " declaration

Answer 25

C# - 309 330 320 306 Bytes

Golfed Version:

private static void F(int aN,int aM){var s=new List<string>();var n=aN.ToString();for(int i=1;i<=aM;i++){int z=n.Length;if(z==1){break;}var a=n;n="";for(int j=0;j<z-1;j++){int r=a[j]-'0'+a[j + 1]-'0';n=n+r;}s.Add(i+": "+n);}int l=s.Count;int p=5;if(l<5){p=l;}for(int k=l-p;k<l;k++){Debug.WriteLine(s[k]);}}

Usage: F(3541,50);

Ungolfed version for readability:

private static void AppendNumbers(int aNum, int aMaxSteps)
    {
        var results = new List<string>();
        var numString = aNum.ToString();
        for (int i = 1; i <= aMaxSteps; i++)
        {
            int stringLength = numString.Length;
            if (stringLength == 1)
            {
                break;
            }
            var a = numString;
            numString = "";
            for (int j = 0; j < stringLength-1; j++)
            {
                int additionResult = a[j]-'0' + (a[j + 1]-'0');
                numString = numString + additionResult;
            }
            results.Add(i+": "+ numString);
        }
        int numberOfResults = results.Count;
        int p = 5;
        if (numberOfResults < 5)
        {
            p = numberOfResults;
        }
        for (int k = numberOfResults - p; k < numberOfResults; k++)
        {
            Debug.WriteLine(results[k]);
        }
    }

Suggestions for improvement are always welcome! ;)

Edit: Removed String.Empty and replaced it with "" to save 10 Bytes.

Edit 2: Thanks to malik for the tipp with the strings!