procedure change_node(var PSP:u);
{обмен первого и предпоследнего элементов списка}
var q,s,t:u;
ch:char; begin
if (PSP=nil) or (PSP^.ukz=nil) or (PSP^.ukz^.ukz=nil) then
begin
WriteLn(‘Обработка невозможна');
Exit end;
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{поиск предпоследнего элемента} q:=PSP;
s:=PSP^.ukz;
while s^.ukz^.ukz<>nil do
{s-указатель на предпосл.элемент} begin
q:=s;
s:=s^.ukz;
end;
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psp |
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if q=PSP then
{особ.случай-обмен 1-го и 2-го элем-ов}
begin q^.ukz:=s^.ukz; s^.ukz:=q; PSP:=s;
Exit end;
Psp,q s
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{общий случай} t:=PSP^.ukz; PSP^.ukz:=s^.ukz; s^.ukz:=t; q^.ukz:=PSP;
PSP:=s; end;
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psp |
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