Merge Two Paragraphs with Removing Duplicated Lines

Question

Challenge

The goal of this challenge is to make a function that takes two paragraphs and output a concatenated result with removing the duplicated overlapped lines due to redundancy (but a single copy of the part of overlapped lines should be kept to avoid information loss). Each input paragraph is with the follows specifications.

• The leading/trailing spaces in each line have been removed.

• No empty line.

The output merged paragraph follows the rules as below.

• Input paragraph 2 is concatenated after input paragraph 1

• If the line(s) from the start of the input paragraph 2 is / are sequenced same (overlapped) as the end of input paragraph 1, just keep single copy of the sequenced duplicated lines.

• The definition of duplicated lines here:

  • The content in two line should be totally the same, no “partial overlapping” cases need to be considered.

  • The content sequence in two blocks of lines should be totally the same.

Example Input and Output

• Inputs

  Input paragraph 1 example:

  Code Golf Stack Exchange is a question and answer site for programming puzzle enthusiasts and code golfers.
  It's built and run by you as part of the Stack Exchange network of Q&A sites.
  With your help, we're working together to build a library of programming puzzles and their solutions.
  We're a little bit different from other sites. Here's how:
  Ask questions, get answers, no distractions
  This site is all about getting answers. It's not a discussion forum. There's no chit-chat.
  

  Input paragraph 2 example:

  We're a little bit different from other sites. Here's how:
  Ask questions, get answers, no distractions
  This site is all about getting answers. It's not a discussion forum. There's no chit-chat.
  Good answers are voted up and rise to the top.
  The best answers show up first so that they are always easy to find.
  The person who asked can mark one answer as "accepted".
  Accepting doesn't mean it's the best answer, it just means that it worked for the person who asked.
  Get answers to practical, detailed questions
  Focus on questions about an actual problem you have faced. Include details about what you have tried and exactly what you are trying to do.
  Not all questions work well in our format. Avoid questions that are primarily opinion-based, or that are likely to generate discussion rather than answers.
  

• Expected Output

  

  The two block of text are the same, so keep single overlapped part after merging.

  

  Code Golf Stack Exchange is a question and answer site for programming puzzle enthusiasts and code golfers.
  It's built and run by you as part of the Stack Exchange network of Q&A sites.
  With your help, we're working together to build a library of programming puzzles and their solutions.
  We're a little bit different from other sites. Here's how:
  Ask questions, get answers, no distractions
  This site is all about getting answers. It's not a discussion forum. There's no chit-chat.
  Good answers are voted up and rise to the top.
  The best answers show up first so that they are always easy to find.
  The person who asked can mark one answer as "accepted".
  Accepting doesn't mean it's the best answer, it just means that it worked for the person who asked.
  Get answers to practical, detailed questions
  Focus on questions about an actual problem you have faced. Include details about what you have tried and exactly what you are trying to do.
  Not all questions work well in our format. Avoid questions that are primarily opinion-based, or that are likely to generate discussion rather than answers.
  

Rules of Challenge

This is code-golf. The answer with the least bytes wins.

Answer 1

Python 3.8 (pre-release), 104 bytes

def o(a,b,i=None):
 while(i:=a[:i].rfind(b[0]))+1:
  if b.find(a[i:])==0:return a[:i]+b
 return a+'\n'+b

Try it online!

I've come up with this as my first ever Code Golf challenge. Defines function o (short for overlay) which returns string a overlayed with string b, or their concatenation if there is no overlap.

It repetitively searches backwards in a for the first letter of b and, if a match is found, compares from that point on in a to the beginning of b until an overlap is found or a has been fully scanned.

Answer 2

Retina 0.8.2, 14 bytes

ms`$(.+)^\1
$1

Try it online! Assumes that neither paragraph will be matched in its entirety. Explanation: The leading $ ensures that the capture begins with a newline, while the inner ^ ensures that it ends with a (possibly the same) newline. It then remains to delete the duplicate.

Answer 3

APL+WIN, 19 bytes

Prompts for the second paragraph followed by the first as nested vectors of lines:

(∨⌿<\x^.=⍉x)⌿x←⊃⎕,⎕

Try it online! Thanks to Dyalog Classic

Answer 4

05AB1E, 13 bytes

.s€»ʒÅ?}θK¹»ì

First input as a list of lines, second as a multi-line string. (Taking multi-line input as a list of lines is allowed by default.)

Try it online.

Would be 1 byte longer if we can take both inputs as multi-line strings: try it online.
Would be 3 bytes shorter if partial lines could also overlap: try it online.

Explanation:

.s          # Get a list of suffices of the first (implicit) input-list of lines
  €         # Map over each suffix:
   »        #  And join them by newlines
    ʒ       # Then filter of these string-suffices:
     Å?     #  And keep the one that the second (implicit) input-string starts with
    }θ      # After the filter: keep only the last/longest suffix
      K     # Remove this overlapping text from the second (implicit) input-string
       ¹»   # Push the first input-list, and join it by newlines
         ì  # And prepend it to the other string
            # (after which the result is output implicitly)

Answer 5

JavaScript (ES6), 52 bytes

I/O format: lists of strings. Expects (b)(a).

b=>g=a=>a.some((s,i)=>b[i]!=s)?[a.shift(),...g(a)]:b

Try it online!

Test cases stolen borrowed from @dingledooper.

Commented

b =>               // anonymous outer function taking the 2nd paragraph b[]
g = a =>           // inner recursive function g taking the 1st paragraph a[]
  a.some((s, i) => // for each line s at position i in a[]:
    b[i] != s      //   truthy if the i-th line of b is not equal to s
  ) ?              // end of some(); if truthy:
    [              //   create an array consisting of:
      a.shift(),   //     the 1st line removed from a[]
      ...g(a)      //     followed by the lines returned by a recursive call
    ]              //   end of array
  :                // else:
    b              //   stop the recursion and return b[]

Answer 6

Python 2, 59 51 bytes

8 bytes thanks to @ovs

Input is taken as two lists of strings.

f=lambda a,b:`a`[:-1]in`b`and b or[a.pop(0)]+f(a,b)

Try it online!

Answer 7

Wolfram Language (Mathematica), 32 31 bytes

{a___,d=b___}±{d,c___}={a,b,c}

Try it online!

Defines an operator ± (PlusMinus).

Mathematica's pattern-matching does the entirety of the work here:

{a___,b___}±{b___,c___}=    (* function of two lists, where (b___) a possibly-empty postfix of the first is a prefix of the second: *):
  {a,b,c}                   (* concatenate. *)

Answer 8

Perl 5 (-0777p), 20 bytes

s/^(.*
)
\1|^
/$1/ms

Try it online!

Answer 9

JavaScript (Node.js), 70 68 bytes

l=(a,b,c)=>b.startsWith(a.slice(c=~~c,-1))?a.slice(0,c)+b:l(a,b,++c)

Try it online!

Answer 10

AWK, ^{28 \$\cdots\$ 85} 84 bytes

Added 44 bytes to fix a bug kindly pointed out by Dominic van Essen.
Added another 13 bytes to fix another bug pointed out by Dominic van Essen and JimmyHu.
Saved a byte thanks to cnamejj!!!

$0 in a&&m&&!h{h=a[$0]+1;next}h&&a[$0]==h{++h;next}!NF{m=1;next}!m{a[$0]=++i}{print}

Try it online!

Inputs the two paragraphs separated by an empty line from stdin.

Answer 11

R, 77 74 71 61 60 bytes

Edit: -3 bytes and bug-fix thanks to Giuseppe, then -1 byte thanks to Robin Ryder

function(p,q){while(any(p!=(s=c(p[0:F],q))[seq(p)]))F=F+1;s}

Try it online!

Tries increasingly long prefixes of p (first paragraph) and joins q (second paragraph) onto them, until one is found whose first elements are equal to the whole of p (this will always happen when the 'prefix' grows to become the entirity of p, of course).

Answer 12

Jelly,  10  8 bytes

-2 bytes thanks to (same method but with a much better choice of atoms!)

ẇÐƤẹ0⁸ṁ;

A dyadic Link accepting lists of lines that yields a list of lines.

Try it online!

How?

ẇÐƤẹ0⁸ṁ; - Link: P1, P2
 ÐƤ      - for postfixes, X, of P1:
ẇ        -   sublist (X) exists in (P2)?
   ẹ0    - indices of 0
     ⁸ṁ  - mould P1 like that
       ; - concatenate P2

Answer 13

Perl 5, 42 bytes

sub f{join($;,@_)=~s,^((.+\n)*)$;\1,$1,mr}

Try it online!

Answer 14

Husk, 11 12 bytes

Edit: +1 byte to fix bug (when first paragraph is entirely within second)

ḟoΠz=³m`+⁰Θḣ

Try it online!

ḟ               # return first list that satisfies:
 oΠ             #   all truthy results of
   z=³          #   comparing each element to each element of arg1 
                # from this list:
      m         # for each of
          Θḣ    # the prefixes of arg1, beginning with the empty list,
       `+⁰      # append arg2

Answer 15

JavaScript (Node.js), 35 bytes

x=>x.replace(/^([^]*)\1^|/m,'$1')

Try it online!

Split two inputs with NUL(\0). Competive even if need to do in function