Spiral Programming

Question

Write a named function or program that accepts a single integer N and prints (to STDOUT) or returns (as a string) the first N bars of the spiral below, beginning with the vertical bar in the center and spiraling clockwise outward.

        _______________
       / _____________ \
      / / ___________ \ \
     / / / _________ \ \ \
    / / / / _______ \ \ \ \
   / / / / / _____ \ \ \ \ \
  / / / / / / ___ \ \ \ \ \ \
 / / / / / / / _ \ \ \ \ \ \ \
/ / / / / / / / \ \ \ \ \ \ \ \
| | | | | | | | | | | | | | | |
\ \ \ \ \ \ \___/ / / / / / / /
 \ \ \ \ \ \_____/ / / / / / /
  \ \ \ \ \_______/ / / / / /
   \ \ \ \_________/ / / / /
    \ \ \___________/ / / /
     \ \_____________/ / /
      \_______________/ /

You may assume that 0 < N <= 278. Your output cannot contain any whitespace in front of the leftmost character of the spiral. You may optionally print a single trailing newline.

For an input of 10, the correct output is

   _
  / \ 
  | | 
\___/

For an input of 2, the correct output is

/
|

For an input of 20, the correct output is

  ___
 / _ \
/ / \ \ 
| | | |
\___/ /

An output that would be incorrect because the leftmost character is preceded by whitespace is

       ___
      / _ \
     / / \ \ 
     | | | |
     \___/ /

The winner is the shortest submission, in bytes.

Answer 1

Python 2, 290 289

It's probably really bad, but I tried :D

The output contains trailing spaces, but that is not forbidden in the spec.

Update: saved 1 byte with changing \n to ;.

m=x=y=c=0
l,f=1,[31*[' ']for t in[0]*31]
for i in[0]*input():
 k=m%4;f[14+y+(2<m<6)][14+x-(m>3)],x,y,c='|/_\\'[k],x+(k>0)*(2*(4>m)-1),y+(k!=2)*(2*(2<m<6)-1),c+1
 if(c==l)*(m%2)+(k==0)+(k==2)*(c==2*l-1+m//3):m,c,l=(m+1)%8,0,l+m//7
print'\n'.join(''.join(e[16-l*2:])for e in f if[' ']*31!=e)

Answer 2

CJam - 156 / 147

L{[W1]{:I0'|{IIW*:J'/}X*[0J'_]X2*I+*[J0_]I1={\}*{J_'\}X*0I0}%L*3/{~_{[UV@]a3$+}{;@}?V@+:V;U@+:U;}/}A,1>fX]ri=_z::e<2<f{[\\]z::-}$_W=0=)S50*a*\{~3$3$=\tt}/N*

Try it online

It works with inputs from 1 to 378 inclusive (100 more than required)

Using the latest committed (publicly available in hg) but unreleased CJam code at the time this challenge was posted, the solution can be shortened to 147 characters:

L{[W1]{:I0'|{IIW*:J'/}X*[0J'_]X2*I+*[J0_]I1={\}*{J_'\}X*0I0}%L*3/{~_{[UV@]a3$+}{;@}?V@+:V;U@+:U;}/}A,1>fX]ri=_:.e<2<f.-$_W=0=)S50*a*\{~3$3$=\tt}/N*

Explanation:

The program iteratively constructs all the spirals as arrays of [x y character] starting with [0 0 '|], gets the requested spiral, adjusts the coordinates so that the minimum x and y are 0, creates a matrix of spaces (with the correct number of rows and 50 columns) then sets the characters from the spiral and joins the rows with newlines.

L                   start with an empty array (spiral no. 0)
{…}A,1>fX           for X in 1..9 (A=10)
                    each X represents a full 360° tour with groups of X /'es and \'es
    [W1]{…}%        transform the array [-1 1] (W=-1) applying the block to each item
                    the block generates a series of triplets dx, dy, character
                    note: dx is down, dy is right; -1 handles ↑↗→↘, 1 handles ↓↙←↖
        :I          store the current item in I
        0'|         add 0 and |, which will form a triplet with the previous I
        {…}X*       repeat X times
            IIW*    add I and -I
            :J'/    also store -I in J, and add /
        [0J'_]      make an array [0 J _]
        X2*I+*      repeat the array X*2+I times
        [J0_]       make an array [J 0 0]
                    (a 0 instead of a character means only changing the position)
        I1={\}*     if I=1, swap the two arrays (the position adjustment is different
                    for the upper and lower horizontal sections)
        {…}X*       repeat X times
            J_'\    add J, J and \
        0I0         add 0, I and 0 (another position adjustment)
    L*              flatten the array (since we added a few inner arrays)
    3/              split into [dx dy char] triplets
    {…}/            for each triplet
        ~_          dump the 3 items on the stack and duplicate the character
        {…}         if the character is not 0
            [UV@]   make an array [U V char] (U and V are initially 0)
                    U represents "x" and V represents "y"
            a3$+    add it as an element to a copy of the previous spiral
        {…}         else
            ;@      pop the character and bring the previous spiral to the top
        ?           end if
        V@+:V;      V+=dy
        U@+:U;      U+=dx
]                   put all the spirals in an array
ri=                 read token, convert to integer and get that spiral
_z::e<              copy the spiral and get a triplet with the minimum values
2<                  keep only the first 2 items (xmin and ymin)
f{…}                for each triplet and the array [xmin ymin]
    [\\]z::-        subtract xmin and ymin from x and y in the triplet
                    (in the latest CJam code this is simply ".-")
$                   sort the spiral (putting the triplets in order by x then y)
_W=0=)              get the maximum (updated) x and increment it
S50*                make a string of 50 spaces
a*                  put it in an array and repeat it xmax+1 times
                    this is the initial matrix of spaces
\                   swap with the spiral
{…}/                for each triplet in the spiral
    ~               dump the 3 items (x y char) on the stack
    3$3$=           copy the matrix and x, and get the x'th row
    \t              swap with the character and put that character in the y'th position
    t               put the modified row in the x'th position in the matrix
N*                  join the matrix rows with newlines

Answer 3

JavaScript (ES6) 257 288 321

Edit Steps merged.
Edit Golfed code fiddling to cut some more char

Build the output iteratively into the r array, keeping track of current x and y position and current direction. When the x or y position is < 0 the whole r array is readjusted.

Main variables:

• r result array or rows
• x,y current position.
• s current direction (0..7) (or current state)
• d current symbol to draw (0..3) -> '|\_/'
• l runnig position on the current sequence (down to 0)
• w current spiral radius (more or less)

F=n=>
  (w=>{
    for(r=b=[],s=y=x=d=0;n--;
      d&&--l||((s=s+1&7,d=s&3)?l=d-2?w:s/2-2+w+w:w+=!s))
      s>0&s<4?++x:s>4?x?--x:r=r.map(v=>' '+v):b+='  ',
      q=r[s>2&s<6?++y:y]||b,
      r[y]=(q+b).slice(0,x)+'|/_\\'[d]+q.slice(x+1),
      s<2|s>6?y?--y:r=[,...r]:x+=!d*2,x-=!d
  })(1)||r.join('\n')

Ungolfed

F=n=>{
  var r=[], s,x,y,d,w,l, q
  for(l=w=1, s=x=y=d=0; n--;)
  {
    if (s>2 && s<6) ++y; // right side, inc y before drawing

    if (x < 0) // too left, adjust
    {
      r = r.map(v=>' '+v) // shift all to right
      ++x; // move current position to right
    }
    if (y < 0) // too up
    {
      r = [q='',...r] // shift all to bottom
      ++y; // move current position to bottom
    }
    q = r[y] || ''; // current row, if undefined convert to empty string
    r[y] = (q+' '.repeat(x)).slice(0,x) + '|/_\\'[d] + q.slice(x+1); // add current symbol in the x column

    if (s<2 || s>6) --y; // left side, dec y after drawing

    if (s>0 && s<4) // always change x after drawing
      ++x;
    else if (s > 4)
      --x;

    --l; // decrement current run
    if (l == 0) // if 0, need to change direction
    {
      s = (s+1) % 8; // change direction
      d = s % 4; // change symbol
      if (d == 0)
      { 
        // vertical direction, adjust x and if at 0 increase radius
        l = 1 // always 1 vertical step
        if (s == 0)
          ++x, ++w
        else
          --x
      }
      else
      {
        if (d != 2)
        {
          l = w; // diaagonal length is always w
        }
        else if (s == 2)
        {
          l = w+w-1 // top is radius * 2 -1
        }
        else
        {
          l = w+w+1 // bottom is radius * 2 +1
        }
      }
    }
  }    
  return r.join('\n')
}  

Test In Firefox/FireBug console (or JSFiddle thx @Rainbolt)

;[1, 2, 10, 20, 155, 278].forEach(x=>console.log(F(x)))

Output

|

/
|

   _
  / \
  | |
\___/

  ___
 / _ \
/ / \ \
| | | |
\___/ /

      ___________
     / _________ \
    / / _______ \ \
   / / / _____ \ \ \
  / / / / ___ \ \ \ \
 / / / / / _ \ \ \ \ \
/ / / / / / \ \ \ \ \ \
| | | | | | | | | | | |
\ \ \ \ \___/ / / / /
 \ \ \ \_____/ / / /
  \ \ \_______/ / /
   \ \_________/ /
    \___________/

        _______________
       / _____________ \
      / / ___________ \ \
     / / / _________ \ \ \
    / / / / _______ \ \ \ \
   / / / / / _____ \ \ \ \ \
  / / / / / / ___ \ \ \ \ \ \
 / / / / / / / _ \ \ \ \ \ \ \
/ / / / / / / / \ \ \ \ \ \ \ \
| | | | | | | | | | | | | | | |
\ \ \ \ \ \ \___/ / / / / / / /
 \ \ \ \ \ \_____/ / / / / / /
  \ \ \ \ \_______/ / / / / /
   \ \ \ \_________/ / / / /
    \ \ \___________/ / / /
     \ \_____________/ / /
      \_______________/ /
      

Answer 4

Pyth, 166 165

I just translated my Python answer to Pyth, with my not-great Pyth skills. The resulting vomit is below.

Jm*31]d*31dK0=G0=H0=Y1VQ X@J++14H&<2K<K6+14-G<3K@"|/_\\"%K4~G*<0%K4-*2>4K1~H*n2%K4-*2&<2K>6K1~Z1I||&qZY%K2!%K4&q2%K4qZ+-*2Y1/K3~Y/K7=K%+1K8=Z0;jbmj>d-16*2Ykfn*31]dTJ