Singly-linked list/Reversal: Difference between revisions
→{{header|Wren}}: prepend Pascal version
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llist = list(1, 2, 3, 4, 5)
revlist = list(5, 4, 3, 2, 1)
</pre>
=={{header|Pascal}}==
==={{header|Free Pascal}}===
Reverting list by reverting the pointers.
<syntaxhighlight lang="pascal">
program RevSingleLinkedList;
type
tdata = string[15];
tpsList = ^tsList;
tsList = record
data:tData;
next : tpsList;
end;
const
cData: array[1..6] of string = ('Big','fjords','vex','quick','waltz','nymph');
var
root : tpsList;
function InitLList(cnt:integer):tpsList;
var
root,tmpList : tpsList;
i : integer;
begin
tmpList := new(tpsList);
root := tmpList;
root^.data := cData[1];
For i := 2 to high(cData) do
begin
tmpList^.next := new(tpsList);
tmpList := tmpList^.next;
tmpList^.data := cData[i];
end;
tmpList^.next := NIL;
InitLList := root;
end;
procedure OutList(root:tpsList);
begin
while root <> NIL do
begin
write(root^.data,' ');
root := root^.next;
end;
writeln;
end;
procedure RevList(var root:tpsList);
var
NextinList,NewNext : tpsList;
begin
if (root = NIL) OR (root^.next = nil) then
EXIT;
NextinList := root^.next;
root^.next := NIL;
while NextinList <> NIL do
begin
//memorize list element before
NewNext := root;
//root set to next element of root
root := NextinList;
//get the next in list
NextinList := NextinList^.next;
//correct pointer to element before
root^.next := NewNext;
end;
end;
procedure DeleteList(var root:tpsList);
var
tmpList : tpsList;
begin
while root <> nil do
begin
tmpList := root^.next;
dispose(root);
root := tmpList;
end;
end;
begin
root := InitLList(100);
OutList(root);
writeln('Reverse 3 times');
RevList(root);OutList(root);
RevList(root);OutList(root);
RevList(root);OutList(root);
DeleteList(root);
OutList(root);
end.</syntaxhighlight>
{{out}}
<pre>
Big fjords vex quick waltz nymph
Reverse 3 times
nymph waltz quick vex fjords Big
Big fjords vex quick waltz nymph
nymph waltz quick vex fjords Big
</pre>
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