Permutations by swapping: Difference between revisions
Permutations by swapping in various BASIC dialents (BASIC256, QBasic, Run BASIC and Yabasic)
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(Permutations by swapping in various BASIC dialents (BASIC256, QBasic, Run BASIC and Yabasic)) |
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2143 Sign: 1
2134 Sign: -1</pre>
=={{header|BASIC}}==
==={{header|BASIC256}}===
{{trans|Free BASIC}}
<lang BASIC256>call perms(3)
print
call perms(4)
end
subroutine perms(n)
dim p((n+1)*4)
for i = 1 to n
p[i] = -i
next i
s = 1
do
print "Perm: [ ";
for i = 1 to n
print abs(p[i]); " ";
next i
print "] Sign: "; s
k = 0
for i = 2 to n
if p[i] < 0 and (abs(p[i]) > abs(p[i-1])) and (abs(p[i]) > abs(p[k])) then k = i
next i
for i = 1 to n-1
if p[i] > 0 and (abs(p[i]) > abs(p[i+1])) and (abs(p[i]) > abs(p[k])) then k = i
next i
if k then
for i = 1 to n #reverse elements > k
if abs(p[i]) > abs(p[k]) then p[i] = -p[i]
next i
if p[k] < 0 then i = k-1 else i = k+1
temp = p[k]
p[k] = p[i]
p[i] = temp
s = -s
end if
until k = 0
end subroutine</lang>
==={{header|QBasic}}===
{{works with|QBasic|1.1}}
{{works with|QuickBasic|4.5}}
{{trans|Free BASIC}}
<lang qbasic>SUB perms (n)
DIM p((n + 1) * 4)
FOR i = 1 TO n
p(i) = -i
NEXT i
s = 1
DO
PRINT "Perm: (";
FOR i = 1 TO n
PRINT ABS(p(i)); "";
NEXT i
PRINT ") Sign: "; s
k = 0
FOR i = 2 TO n
IF p(i) < 0 AND (ABS(p(i)) > ABS(p(i - 1))) AND (ABS(p(i)) > ABS(p(k))) THEN k = i
NEXT i
FOR i = 1 TO n - 1
IF p(i) > 0 AND (ABS(p(i)) > ABS(p(i + 1))) AND (ABS(p(i)) > ABS(p(k))) THEN k = i
NEXT i
IF k THEN
FOR i = 1 TO n 'reverse elements > k
IF ABS(p(i)) > ABS(p(k)) THEN p(i) = -p(i)
NEXT i
'if p(k) < 0 then i = k-1 else i = k+1
i = k + SGN(p(k))
SWAP p(k), p(i)
'temp = p(k)
'p(k) = p(i)
'p(i) = temp
s = -s
END IF
LOOP UNTIL k = 0
END SUB
perms (3)
PRINT
perms (4)</lang>
==={{header|Run BASIC}}===
{{trans|Free BASIC}}
<lang runbasic>sub perms n
dim p((n+1)*4)
for i = 1 to n : p(i) = i*-1 : next i
s = 1
while 1
print "Perm: [ ";
for i = 1 to n
print abs(p(i)); " ";
next i
print "] Sign: "; s
k = 0
for i = 2 to n
if p(i) < 0 and (abs(p(i)) > abs(p(i-1))) and (abs(p(i)) > abs(p(k))) then k = i
next i
for i = 1 to n-1
if p(i) > 0 and (abs(p(i)) > abs(p(i+1))) and (abs(p(i)) > abs(p(k))) then k = i
next i
if k then
for i = 1 to n 'reverse elements > k
if abs(p(i)) > abs(p(k)) then p(i) = p(i)*-1
next i
if p(k) < 0 then i = k-1 else i = k+1 'swap K with element looked at
temp = p(k)
p(k) = p(i)
p(i) = temp
s = s*-1 'alternate signs
end if
if k = 0 then exit while
wend
end sub
call perms 3
print
call perms 4</lang>
==={{header|Yabasic}}===
{{trans|Free BASIC}}
<lang freebasic>perms(3)
print
perms(4)
end
sub perms(n)
dim p((n+1)*4)
for i = 1 to n
p(i) = -i
next i
s = 1
repeat
print "Perm: [ ";
for i = 1 to n
print abs(p(i)), " ";
next i
print "] Sign: ", s
k = 0
for i = 2 to n
if p(i) < 0 and (abs(p(i)) > abs(p(i-1))) and (abs(p(i)) > abs(p(k))) k = i
next i
for i = 1 to n-1
if p(i) > 0 and (abs(p(i)) > abs(p(i+1))) and (abs(p(i)) > abs(p(k))) k = i
next i
if k then
for i = 1 to n //reverse elements > k
if abs(p(i)) > abs(p(k)) p(i) = -p(i)
next i
i = k + sig(p(k))
temp = p(k)
p(k) = p(i)
p(i) = temp
s = -s
endif
until k = 0
end sub</lang>
=={{header|BBC BASIC}}==
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