Can't see the forest for the trees

Question

Write a program or function that draws a tree of trees, thus constructing a forest.

The trees are drawn like stacking a pyramid. The first (top) row contains 1 tree, the next row down contains 2 (for a total of 3), the next contains 3 (for a total of 6), and so on. If there aren't enough trees to complete a full row, fill it to the left and leave the spots on the right empty. Additionally, lower-level trees slightly overlap upper-level trees due to their placement.

This is a forest of size 1

  /\
 //\\
///\\\
  ||
  ||

This is a forest of size 2

      /\
     //\\
  /\///\\\
 //\\ ||
///\\\||
  ||
  ||

This is a forest of size 3

      /\
     //\\
  /\///\\\/\
 //\\ || //\\
///\\\||///\\\
  ||      ||
  ||      ||

This is a forest of size 4

          /\
         //\\
      /\///\\\/\
     //\\ || //\\
  /\///\\\||///\\\
 //\\ ||      ||
///\\\||      ||
  ||
  ||

This is a forest of size 5 (note the top of the fifth tree is covering the trunk of the first tree)

          /\
         //\\
      /\///\\\/\
     //\\ || //\\
  /\///\\\/\///\\\
 //\\ || //\\ ||
///\\\||///\\\||
  ||      ||
  ||      ||

(skip a few)
This is a forest of size 8 (extending the pattern)

              /\
             //\\
          /\///\\\/\
         //\\ || //\\
      /\///\\\/\///\\\/\
     //\\ || //\\ || //\\
  /\///\\\/\///\\\||///\\\
 //\\ || //\\ ||      ||
///\\\||///\\\||      ||
  ||      ||
  ||      ||

and so on.

Input

A single positive integer in any convenient format, n > 0.

Output

An ASCII-art representation of the forest, following the above rules. Leading/trailing newlines or other whitespace are optional, provided that the trees all line up appropriately.

Rules

• Either a full program or a function are acceptable. If a function, you can return the output rather than printing it.
• Standard loopholes are forbidden.
• This is code-golf so all usual golfing rules apply, and the shortest code (in bytes) wins.

Answer 1

Haskell 310 bytes

w i=putStr$unlines$reverse$b i 0 0[][]
b 0 _ _ w r=e w r
b c l 0 w r=b c(l+1)l(e w r)[]
b c l p w r=b(c-1)l(p-1)w(n(++)["  ||    ","  ||    ","///\\\\\\  "," //\\\\   ","  /\\    "]r)
e w r=t++n(n d)(map(\t->"    "++t)w)c where(t,c)=splitAt 2 r
n f(a:c)(b:d)=f a b:n f c d
n _ a[]=a
n _ _ a=a
d d ' '=d
d _ d=d

Call it with w 5, for example.

Here the uncompressed code:

-- TreeTree
-- by Gerhard
-- 12 February 2017

module TreeTree (wood,test) where

type Tree = [String]

-- Test cases
test = do
 wood 0
 wood 1
 wood 2
 wood 3
 wood 4
 wood 5

-- build wood
wood :: Int -> IO ()
wood i = printTree $ buildWood i 0 0 [] []

-- Prints the trees
printTree :: Tree -> IO ()
printTree = putStr . unlines . reverse

-- build wood
buildWood :: Int -> Int -> Int -> Tree -> Tree -> Tree
buildWood 0 _ _ w r = concatTree w r 
buildWood c l 0 w r = buildWood c (l+1) l (concatTree w r) []
buildWood c l p w r = buildWood (c-1) l (p-1) w (addTree r)

-- indent definition
space :: String
space = "    "

-- tree definition
tree :: Tree
tree = reverse [
 "  /\\    ",
 " //\\\\   ",
 "///\\\\\\  ",
 "  ||    ",
 "  ||    "]

-- Add a Tree on the left side
addTree :: Tree -> Tree
addTree = match (++) tree

-- add tree row at the bottom of the wood
concatTree :: Tree -> Tree -> Tree
concatTree w r = trunk ++ matched
 where
  wood = grow w
  (trunk, crown) = splitAt 2 r 
  matched = matchTree wood crown

-- elnarge forrest on the left side to match next tree line
grow :: Tree -> Tree
grow = map (\t -> space ++ t)

-- match
match :: (a -> a -> a) -> [a] -> [a] -> [a]
match f (a:az) (b:bz) = f a b : match f az bz
match _ a [] = a
match _ _ a  = a

-- match trees
matchTree :: Tree -> Tree -> Tree
matchTree = match matchLine

-- match lines
matchLine :: String -> String -> String
matchLine = match matchChar

-- match chars
matchChar :: Char -> Char -> Char
matchChar c ' ' = c
matchChar _ c   = c

-- End

Answer 2

C++ (on Windows), 330 312 308 304 303 bytes

#import<cstdio>
#import<windows.h>
#define P(x,y,s)SetConsoleCursorPosition(GetStdHandle(-11),{X+x,Y+y});puts(s);
int X,Y,R,r,c;t(){P(2,-2,"/\\")P(1,-1,"//\\\\")P(0,0,"///\\\\\\")P(2,1,"||")P(2,2,"||")}f(int n){for(c=R=r=1;c<n;c+=++R);for(;r;r++)for(c=0;++c<r+1;){X=(R-r-2)*4+c*8;Y=r*2;t();r=--n?r:-1;}}

Call with:

int main()
{
    f(8);
}

Answer 3

JavaScript (ES6), 357 297 276 bytes

f=
n=>{a=`  /\\`;d=`///\\\\\\`;b=d+`/\\`;c=` //\\\\ ||`;d+=`||`;e=`
`;r=`repeat`;s=``;for(i=1;n>i;n-=i++)s=(s+a+b[r](i-1)+e+c[r](i)).replace(/^/gm,`    `)+e;return(s+a+b[r](n-1)+d[r](i-=n)+e+c[r](n)+(s=`      ||`[r](i))+e+d[r](n)+s+(s=e+`  ||    `[r](n))+s).replace(/\|.$/gm,``)}

<input type=number min=1 oninput=o.textContent=f(this.value)><pre id=o>

Edit: Saved 21 bytes thanks to @KritixiLithos.

Answer 4

Javascript 418 377 bytes

Thanks to @Kritixi Lithos for helping golf off 39 bytes

x=>{s='';for(t=0;++t<x;x-=t);q='//\\\\';z="///\\\\\\";h="/\\";t--;for(i=0;i<t;i++){a=4*(t-i)+1;s+=" "[w="repeat"](a+1)+h+(z+h)[w](i)+`
`+" "[w](a)+q+(" || "+q)[w](i)+`
`}c=t-x+1>0?t-x+1:0;return x?s+"  "+(h+z)[w](--x)+h+(c?(z+"||")[w](c-1)+z:'')+`
 `+q+(" || "+q)[w](x)+" ||     "[w](c)+`
`+(z+"||")[w](x)+z+(c?"||"+"      ||"[w](c-1):'')+`
`+("  ||    "[w](x+1)+`
`)[w](2):''}

Try it Online

Answer 5

C (on Windows), 297 295 294 bytes

#import<windows.h>
#define P(x,y,s)C.X=X+x;C.Y=Y+y;SetConsoleCursorPosition(GetStdHandle(-11),C);puts(s);
COORD C;X,Y,R,r,c;t(){P(2,-2,"/\\")P(1,-1,"//\\\\")P(0,0,"///\\\\\\")P(2,1,"||")P(2,2,"||")}f(n){for(c=R=r=1;c<n;c+=++R);for(;r;r++)for(c=0;++c<r+1;){X=(R-r-2)*4+c*8;Y=r*2;t(r=--n?r:-1);}}

Similar to my C++ answer, but I posted this because it's somewhat shorter in C.