## Independence Day weekend puzzler

on 3 Jul 2011

### Fangjun Jiang (view profile)

Inspired by an assignment in my son's Java programming class:

Write a one-liner that takes as input an array of numbers (e.g. x = [1 2 3]) and which outputs an array of integers that is "incremented" properly, (in this case, y = [1 2 4]).

Examples of proper input/output:

x = [1 9 1 9] ----> y = [1 9 2 0]

and

x = [9 9 9] ----> y = [1 0 0 0]

No semicolons allowed in your one line!

the cyclist

### the cyclist (view profile)

on 4 Jul 2011

I only intended it to be for "smallish" vectors of numbers, but feel free to create whatever conditions you want, for maximum enjoyment.

Paulo Silva

### Paulo Silva (view profile)

on 4 Jul 2011

+1 vote for the interesting puzzler, it's the first vote!
Please vote on it if you found it interesting and you want more of them.

Fangjun Jiang

on 4 Jul 2011

Sure. +1

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### Fangjun Jiang (view profile)

on 3 Jul 2011

I like this Golf challenge. Inspired by Paulo's entry.

```num2str(str2num(sprintf('%d',x))+1)-'0'
```

is shorter.

### Jan Simon (view profile)

on 3 Jul 2011

My submission is neither a one-liner nor free of semicolons. But the total number of lines and semicolons is less than in STR2NUM and NUM2STR, which have 86 and 217 lines and call INT2STR in addtion.

```n = length(x);
q = find(x ~= 9, 1, 'last');
if isempty(q)    % [9, 9, 9, ...]
x = 1;
x(n + 1) = 0;  % or x = [1, zeros(1, n)]
else             % Any non-9 is found
x = [x(1:q - 1), x(q) + 1, zeros(1, n - q)];
end
```

David Young

### David Young (view profile)

on 4 Jul 2011

This works for long vectors (thousands of elements).

### bym (view profile)

on 3 Jul 2011

kind of a hybrid:

```sprintf('%d',sum(x.*10.^(numel(x)-1:-1:0))+1)-'0'
```

David Young

### David Young (view profile)

on 4 Jul 2011

Jan: my earlier answer uses only built-in functions.

Jan Simon

on 4 Jul 2011

David Young

### David Young (view profile)

on 4 Jul 2011

@Jan: The one that starts with a call to diff

### Andrei Bobrov (view profile)

on 3 Jul 2011

```str2num(num2str(10.^(length(x)-1:-1:0)*x'+1)')'
```

```z = 10.^(numel(x)-1:-1:0)*x'+1
y = round(rem(fix(z.*10.^-(fix(log10(z)):-1:0))*.1,1)*10)
```

bym

### bym (view profile)

on 4 Jul 2011

+1 vote for the 'z' solution; compact & elegant

Andrei Bobrov

### Andrei Bobrov (view profile)

on 4 Jul 2011

@proecsm, thanks!

### David Young (view profile)

on 3 Jul 2011

One-liner, avoiding string operations:

```diff([0 (floor((sum(x.*10.^(length(x)-1:-1:0))+1) ./ 10.^(floor(log10(sum(x.*10.^(length(x)-1:-1:0))+1)):-1:0))) .* 10.^(floor(log10(sum(x.*10.^(length(x)-1:-1:0))+1)):-1:0)]) ./ 10.^(floor(log10(sum(x.*10.^(length(x)-1:-1:0))+1)):-1:0)
```

EDIT: This is only one line of code, even though formatting on the Answers web page makes it look like 4 lines.

David Young

### David Young (view profile)

on 4 Jul 2011

This fails if there are more than about 16 elements in the vector, because you only get about 16 significant figures in a double.

Jan Simon

### Jan Simon (view profile)

on 4 Jul 2011

+1: A one-liner without calls to other M-files and therefore even no hidden semicolons.

David Young

on 4 Jul 2011

Thanks Jan!

### Paulo Silva (view profile)

on 3 Jul 2011

```x=[1 2 3]; %example input
xr=num2str(str2num(strrep(num2str(x),' ',''))+1)-'0'
%xr =[1 2 3 4]
```

### the cyclist (view profile)

on 3 Jul 2011

Here's one just a bit shorter than andrei bobrov's [using numel() to trim one character from length()]:

```str2num(num2str(10.^(numel(x)-1:-1:0)*x'+1)')'
```

Anything shorter?!

### David Young (view profile)

on 4 Jul 2011

Also one line of code (formatting for the web page will display it over more than one line of text):

```double(regexprep(char(x), {['([' char(0:8) ']?)(' char(9) '*)\$'] ['^(' char(0) '+)\$']}, {'\${char(\$1+1)}\${regexprep(\$2,char(9),char(0))}' [char(1) '\$1']}))
```

David Young

### David Young (view profile)

on 4 Jul 2011

This one works for long vectors with thousdands of elements (my arithmetic-based solution doesn't).

### David Young (view profile)

on 4 Jul 2011

I'm sorry about this one - it's somewhat over the top, and I promise I won't do any more. However, since I think it's a different approach to the others (arithmetic operations but no powers of 10!), here it is:

```[ones(1, sum(x)==9*length(x)) x(1:length(x)-sum(cumsum(fliplr(x)) == 9*(1:length(x)))-1) repmat(x(max(1, length(x)-sum(cumsum(fliplr(x)) == 9*(1:length(x)))))+1, 1, sum(x)~=9*length(x)) zeros(1, sum(cumsum(fliplr(x)) == 9*(1:length(x))))]
```

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