Longest common prefix: Difference between revisions

</pre>

=={{header|Action!}}==

<lang Action!>DEFINE PTR="CARD"

BYTE Func Equals(CHAR ARRAY a,b)

BYTE i

IF a(0)#b(0) THEN

RETURN (0)

FI

FOR i=1 TO a(0)

DO

IF a(i)#b(i) THEN

RETURN (0)

FI

OD

RETURN (1)

BYTE FUNC CommonLength(PTR ARRAY texts BYTE count)

CHAR ARRAY t

BYTE i,len

IF count=0 THEN

RETURN (0)

FI

len=255

FOR i=0 TO count-1

DO

t=texts(i)

IF t(0)<len THEN

len=t(0)

FI

OD

RETURN (len)

PROC Prefix(PTR ARRAY texts BYTE count CHAR ARRAY res)

CHAR ARRAY t(100)

BYTE i,len,found

IF count=1 THEN

SCopy(res,texts(0))

RETURN

FI

len=CommonLength(texts,count)

WHILE len>0

DO

SCopyS(res,texts(0),1,len)

found=1

FOR i=1 TO count-1

DO

SCopyS(t,texts(i),1,len)

IF Equals(res,t)#1 THEN

found=0 EXIT

FI

OD

IF found THEN

RETURN

FI

len==-1

OD

res(0)=0

RETURN

PROC Test(PTR ARRAY texts BYTE count)

BYTE i

CHAR ARRAY res(100)

Prefix(texts,count,res)

Print("lcp(")

IF count>0 THEN

FOR i=0 TO count-1

DO

PrintF("""%S""",texts(i))

IF i<count-1 THEN

Print(",")

FI

OD

FI

PrintF(")=""%S""%E",res)

RETURN

PROC Main()

CHAR ARRAY

t1="interspecies", t2="interstellar", t3="interstate",

t4="throne", t5="throne", t6="dungeon", t7="",

t8="prefix", t9="suffix", t10="foo", t11="foobar"

PTR ARRAY texts(20)

texts(0)=t1 texts(1)=t2 texts(2)=t3

Test(texts,3)

texts(0)=t4 texts(1)=t5

Test(texts,2)

texts(0)=t4 texts(1)=t6

Test(texts,2)

texts(0)=t4 texts(1)=t7 texts(2)=t5

Test(texts,3)

texts(0)=t7

Test(texts,1)

Test(texts,0)

texts(0)=t8 texts(1)=t9

Test(texts,2)

texts(0)=t10 texts(1)=t11

Test(texts,2)

RETURN</lang>

{{out}}

[https://gitlab.com/amarok8bit/action-rosetta-code/-/raw/master/images/Longest_common_prefix.png Screenshot from Atari 8-bit computer]

<pre>

lcp("interspecies","interstellar","interstate")="inters"

lcp("throne","throne")="throne"

lcp("throne","dungeon")=""

lcp("throne","","throne")=""

lcp("")=""

lcp()=""

lcp("prefix","suffix")=""

lcp("foo","foobar")="foo"