Ðåôåðàò: Îñíîâíûå ïîíÿòèÿ àëãîðèòìè÷åñêîãî ÿçûêà
pBegin L-->¦ NIL ¦<--- pEnd ¦ NIL ¦<--- pAux
L=====- L=====-
pBegin^.pNext:=pAux;
ã=====¬ ã=====¬ ã=====¬ ã=====¬ ã=====¬
¦ *--¦---¬ ¦ D1 ¦ ----¦--* ¦ ¦ ¦ ----¦--* ¦
L=====- ¦ ¦=====¦ ¦ L=====- ¦=====¦ ¦ L=====-
pBegin L-->¦ * ¦<--- pEnd ¦ NIL ¦<--- pAux
L=====- L=====-
¦ ^
¦ ¦
L----------------------------
pEnd:=pAux;
ã=====¬ ã=====¬ ã=====¬ ã=====¬ ã=====¬
¦ *--¦---¬ ¦ D1 ¦ ¦ *--¦---¬ ¦ ¦ ----¦--* ¦
L=====- ¦ ¦=====¦ L=====- ¦ ¦=====¦ ¦ L=====-
pBegin L-->¦ * ¦ pEnd L-->¦ NIL ¦<--- pAux
L=====- L=====-
¦ ^
¦ ¦
L----------------------------
pEnd^.D:=D2;
ã=====¬ ã=====¬ ã=====¬ ã=====¬
¦ *--¦---¬ ¦ D1 ¦ ¦ D2 ¦ ----¦--* ¦
L=====- ¦ ¦=====¦ ¦=====¦ ¦ L=====-
pBegin L-->¦ *--¦-------------------->¦ NIL ¦<--- pEnd
L=====- L=====-
Äîáàâëåíèå ïîñëåäóþùèõ êîìïîíåíò ïðîèçâîäèòñÿ àíàëîãè÷íî.
Âûáîðêà êîìïîíåíòû èç î÷åðåäè îñóùåñòâëÿåòñÿ èç íà÷àëà î÷åðåäè,
îäíîâðåìåííî êîìïîíåíòà èñêëþ÷àåòñÿ èç î÷åðåäè. Ïóñòü â ïàìÿòè ÝÂÌ
ñôîðìèðîâàíà î÷åðåäü, ñîñòîÿùàÿ èç òðåõ ýëåìåíòîâ:
ã=====¬ ã=====¬ ã=====¬ ã=====¬ ã=====¬
¦ *--¦---¬ ¦ D1 ¦ ¦ D2 ¦ ¦ D3 ¦ ----¦--* ¦
L=====- ¦ ¦=====¦ ¦=====¦ ¦=====¦ ¦ L=====-
pBegin L-->¦ *--¦------>¦ *--¦------>¦ NIL ¦<--- pEnd
L=====- L=====- L=====-
Âûáîðêà êîìïîíåíòû âûïîëíÿåòñÿ ñëåäóþùèìè îïåðàòîðàìè:
D1:=pBegin^.D;
pBegin:=pBegin^.pNext;
ã=====¬ ã=====¬ ã=====¬ ã=====¬ ã=====¬
¦ *--¦---¬ ¦ D1 ¦ ¦ D2 ¦ ¦ D3 ¦ ----¦--* ¦
L=====- ¦ ¦=====¦ ¦=====¦ ¦=====¦ ¦ L=====-
pBegin ¦ ¦ ¦ --->¦ *--¦------>¦ NIL ¦<--- pEnd
¦ L=====- ¦ L=====- L=====-
¦ ¦
L--------------
Ïðèìåð. Ñîñòàâèòü ïðîãðàììó, êîòîðàÿ ôîðìèðóåò î÷åðåäü, äîáàâëÿåò
â íåå ïðîèçâîëüíîå êîëè÷åñòâî êîìïîíåíò, à çàòåì ÷èòàåò âñå êîìïîíåí-
òû è âûâîäèò èõ íà ýêðàí äèñïëåÿ.  êà÷åñòâå äàííûõ âçÿòü ñòðîêó ñèì-
âîëîâ. Ââîä äàííûõ - ñ êëàâèàòóðû äèñïëåÿ, ïðèçíàê êîíöà ââîäà -
ñòðîêà ñèìâîëîâ END.
Program QUEUE;
uses Crt;
type
Alfa= String[10];
PComp= ^Comp;
Comp= record
sD:Alfa;
pNext:PComp
end;
var
pBegin, pEnd: PComp;
sC: Alfa;
Procedure CreateQueue(var pBegin,pEnd: PComp; var sC: Alfa);
begin
New(pBegin);
pBegin^.pNext:=NIL;
pBegin^.sD:=sC;
pEnd:=pBegin
end;
Procedure AddQueue(var pEnd:PComp; var sC:Alfa);
var pAux: PComp;
begin
New(pAux);
pAux^.pNext:=NIL;
pEnd^.pNext:=pAux;
pEnd:=pAux;
pEnd^.sD:=sC
end;
Procedure DelQueue(var pBegin: PComp; var sC: Alfa);
begin
sC:=pBegin^.sD;
pBegin:=pBegin^.pNext
end;
begin
Clrscr;
writeln(' ÂÂÅÄÈ ÑÒÐÎÊÓ ');
readln(sC);
CreateQueue(pBegin,pEnd,sC);
repeat
writeln(' ÂÂÅÄÈ ÑÒÐÎÊÓ ');
readln(sC);
AddQueue(pEnd,sC)
until sC='END';
writeln(' ***** ÂÛÂÎÄ ÐÅÇÓËÜÒÀÒÎÂ *****');
repeat
DelQueue(pBegin,sC);
writeln(sC);
until pBegin=NIL
end.
40. Ë È Í Å É Í Û Å Ñ Ï È Ñ Ê È
 ñòåêè èëè î÷åðåäè êîìïîíåíòû ìîæíî äîáàâëÿòü òîëüêî â êàêîé -
ëèáî îäèí êîíåö ñòðóêòóðû äàííûõ, ýòî îòíîñèòñÿ è ê èçâëå÷åíèþ êîìïî-
íåíò.
Ñâÿçíûé (ëèíåéíûé) ñïèñîê ÿâëÿåòñÿ ñòðóêòóðîé äàííûõ, â ïðîèçâîëü-
íî âûáðàííîå ìåñòî êîòîðîãî ìîãóò âêëþ÷àòüñÿ äàííûå, à òàêæå èçûìàòü-
ñÿ îòòóäà.
Êàæäàÿ êîìïîíåíòà ñïèñêà îïðåäåëÿåòñÿ êëþ÷îì. Îáû÷íî êëþ÷ - ëèáî
÷èñëî, ëèáî ñòðîêà ñèìâîëîâ. Êëþ÷ ðàñïîëàãàåòñÿ â ïîëå äàííûõ êîìïî-
íåíòû, îí ìîæåò çàíèìàòü êàê îòäåëüíîå ïîëå çàïèñè, òàê è áûòü ÷àñòüþ
ïîëÿ çàïèñè.
Îñíîâíûå îòëè÷èÿ ñâÿçíîãî ñïèñêà îò ñòåêà è î÷åðåäè ñëåäóþùèå:
-äëÿ ÷òåíèÿ äîñòóïíà ëþáàÿ êîìïîíåíòà ñïèñêà;
-íîâûå êîìïîíåíòû ìîæíî äîáàâëÿòü â ëþáîå ìåñòî ñïèñêà;
-ïðè ÷òåíèè êîìïîíåíòà íå óäàëÿåòñÿ èç ñïèñêà.
Íàä ñïèñêàìè âûïîëíÿþòñÿ ñëåäóþùèå îïåðàöèè:
-íà÷àëüíîå ôîðìèðîâàíèå ñïèñêà (çàïèñü ïåðâîé êîìïîíåíòû);
-äîáàâëåíèå êîìïîíåíòû â êîíåö ñïèñêà;
-÷òåíèå êîìïîíåíòû ñ çàäàííûì êëþ÷îì;
-âñòàâêà êîìïîíåíòû â çàäàííîå ìåñòî ñïèñêà (îáû÷íî ïîñëå êîìïî-
íåíòû ñ çàäàííûì êëþ÷îì);
-èñêëþ÷åíèå êîìïîíåíòû ñ çàäàííûì êëþ÷îì èç ñïèñêà.
Äëÿ ôîðìèðîâàíèÿ ñïèñêà è ðàáîòû ñ íèì íåîáõîäèìî èìåòü ïÿòü ïåðå-
ìåííûõ òèïà óêàçàòåëü, ïåðâàÿ èç êîòîðûõ îïðåäåëÿåò íà÷àëî ñïèñêà,
âòîðàÿ - êîíåö ñïèñêà, îñòàëüíûå- âñïîìîãàòåëüíûå.
Îïèñàíèå êîìïîíåíòû ñïèñêà è ïåðåìåííûõ òèïà óêàçàòåëü äàäèì ñëå-
äóþùèì îáðàçîì:
type
PComp= ^Comp;
Comp= record
D:T;
pNext:PComp
end;
var
pBegin, pEnd, pCKey, pPreComp, pAux: PComp;
ãäå pBegin - óêàçàòåëü íà÷àëà ñïèñêà, pEnd - óêàçàòåëü êîíöà ñïèñêà,
pCKey, pPreComp, pAux - âñïîìîãàòåëüíûå óêàçàòåëè.
Íà÷àëüíîå ôîðìèðîâàíèå ñïèñêà, äîáàâëåíèå êîìïîíåíò â êîíåö ñïèñêà
âûïîëíÿåòñÿ òàê æå, êàê è ïðè ôîðìèðîâàíèè î÷åðåäè.
ã=====¬ ã=====¬ ã=====¬ ã=====¬ ã=====¬ ã=====¬
¦ *--¦-¬ ¦ D1 ¦ ¦ D2 ¦ ¦ DN1 ¦ ¦ DN ¦ --¦--* ¦
L=====- ¦ ¦=====¦ ¦=====¦ ¦=====¦ ¦=====¦ ¦ L=====-
pBegin L-->¦ *--¦--->¦ *--¦-....->¦ *--¦--->¦ NIL ¦<-- pEnd
L=====- L=====- L=====- L=====-
Äëÿ ÷òåíèÿ è âñòàâêè êîìïîíåíòû ïî êëþ÷ó íåîáõîäèìî âûïîëíèòü ïî-
èñê êîìïîíåíòû ñ çàäàííûì êëþ÷îì:
pCKey:=pBegin;
while (pCKey<>NIL) and (Key<>pCKey^.D) DO
pCKey:=pCKey^.pNext;
Çäåñü Key - êëþ÷, òèï êîòîðîãî ñîâïàäàåò ñ òèïîì äàííûõ êîìïîíåíòû.
Ïîñëå âûïîëíåíèÿ ýòèõ îïåðàòîðîâ óêàçàòåëü pÑKey áóäåò îïðåäåëÿòü
êîìïîíåíòó ñ çàäàííûì êëþ÷îì èëè òàêàÿ êîìïîíåíòà íå áóäåò íàéäåíà.
Ïóñòü pCKey îïðåäåëÿåò êîìïîíåíòó ñ çàäàííûì êëþ÷îì. Âñòàâêà íîâîé
êîìïîíåíòû âûïîëíÿåòñÿ ñëåäóþùèìè îïåðàòîðàìè:
New(pAux); ã===¬
pAux^.D:= DK1; ---¦-* ¦
¦ L===-
¦ pCKey
¦
ã===¬ ã===¬ ã===¬ ã===¬ ã===¬ ã===¬
¦ *-¦--¬ ¦D1 ¦ ¦Key¦ ¦KK1¦ ¦DN ¦ ---¦-* ¦
L===- ¦ ¦===¦ ¦===¦ ¦===¦ ¦===¦ ¦ L===-
pBegin L->¦ *-¦-...->¦ *-¦---->¦ *-¦-...->¦NIL¦<-- pEnd
L===- L===- L===- L===-
ã===¬ ã===¬
¦DK1¦ ---¦-* ¦
¦===¦ ¦ L===-
¦ ¦<-- pAux
L===-
pAux^.pNext:=pCKey^.pNext;
pCKey^.pNext:=pAux;
ã===¬
---¦-* ¦
¦ L===-
¦ pCKey
¦
ã===¬ ã===¬ ã===¬ ã===¬ ã===¬ ã===¬
¦ *-¦--¬ ¦D1 ¦ ¦Key¦ ¦KK1¦ ¦DN ¦ ---¦-* ¦
L===- ¦ ¦===¦ ¦===¦ ¦===¦ ¦===¦ ¦ L===-
pBegin L->¦ *-¦-...->¦ * ¦ ¦ *-¦-...->¦NIL¦<-- pEnd
L===- L===- L===- L===-
¦ ^
¦ ¦ ã===¬ ã===¬
¦ ¦ ¦DK1¦ ---¦-* ¦
¦ L----------¦===¦ ¦ L===-
L------------------->¦-* ¦<-- pAux
L===-
Äëÿ óäàëåíèÿ êîìïîíåíòû ñ çàäàííûì êëþ÷îì íåîáõîäèìî ïðè ïîèñêå
íóæíîé êîìïîíåíòû ïîìíèòü àäðåñ ïðåäøåñòâóþùåé:
pCKey:=pBegin;
while (pCKey<>NIL) and (Key<>pCKey^.D) do
begin
pPreComp:=pCKey;
pCKey:=pCKey^.pNext
end;
Çäåñü óêàçàòåëü pCKey îïðåäåëÿåò êîìïîíåíòó ñ çàäàííûì êëþ÷îì, óêàçà-
òåëü pPreComp ñîäåðæèò àäðåñ ïðåäèäóùåé êîìïîíåíòû.
Óäàëåíèå êîìïîíåíòû ñ êëþ÷îì Key âûïîëíÿåòñÿ îïåðàòîðîì:
pPreComp^.pNext:=pCKey^.pNext;
pPreComp pCKey
ã===¬ ã===¬
¦ * ¦ ¦ * ¦
L===- L===-
¦ ¦
¦ ¦
¦ ¦
ã===¬ ã===¬ ã===¬ ã===¬ ã===¬ ã===¬ ã===¬
¦ *-¦--¬ ¦D1 ¦ ¦KK1¦ ¦Key¦ ¦KK2¦ ¦DN ¦ ---¦-* ¦
L===- ¦ ¦===¦ ¦===¦ ¦===¦ ¦===¦ ¦===¦ ¦ L===-
pBegin L->¦ *-¦-...->¦ *-¦-¬ ¦ *-¦--->¦ *-¦-...->¦NIL¦<-- pEnd
L===- L===- ¦ L===- L===- L===-
¦ ^
¦ ¦
L---------------
Ïðèìåð. Ñîñòàâèòü ïðîãðàììó, êîòîðàÿ ôîðìèðóåò ñïèñîê, äîáàâëÿåò â
íåãî ïðîèçâîëüíîå êîëè÷åñòâî êîìïîíåíò, âûïîëíÿåò âñòàâêó è óäàëåíèå
êîìïîíåíòû ïî êëþ÷ó, à çàòåì ÷èòàåò è âûâîäèò âåñü ñïèñîê íà ýêðàí
äèñïëåÿ.  êà÷åñòâå äàííûõ âçÿòü ñòðîêó ñèìâîëîâ. Ââîä äàííûõ - ñ
êëàâèàòóðû äèñïëåÿ, ïðèçíàê êîíöà ââîäà - ñòðîêà ñèìâîëîâ END.
Program LISTLINKED;
uses Crt;
type
Alfa= String[10];
PComp= ^Comp;
Comp= record
sD:Alfa;
pNext:PComp
end;
var
pBegin, pEnd, pAux, pCKey, pPreComp: PComp;
sC, sKey: Alfa;
bCond: Boolean;
Procedure CreateLL(var pBegin,pEnd: PComp; var sC: Alfa);
begin
New(pBegin);
pBegin^.pNext:=NIL;
pBegin^.sD:=sC;
pEnd:=pBegin
end;
Procedure AddLL(var pEnd: PComp; var sC: Alfa);
var pAux: PComp;
begin
New(pAux);
pAux^.pNext:=NIL;
pEnd^.pNext:=pAux;
pEnd:=pAux;
pEnd^.sD:=sC
end;
Procedure Find(var sKey: Alfa; var pBegin,pCKey,pPreComp: PComp;
var bCond: Boolean);
begin
pCKey:=pBegin;
while (pCKey <> NIL) and (sKey <> pCKey^.D) do
begin
pPreComp:=pCKey;
pCKey:=pCKey^.pNext
end;
if (pCKey = NIL) and (sKey <> pCKey^.sD) then bCond:=FALSE
else bCond:=TRUE
end;
Procedure InsComp(var sKey,sC: Alfa);
var pAux:PComp;
begin
Find(sKey,pBegin,pCKey,pPreComp,bCond);
New(pAux);
pAux^.sD:=sC;
pAux^.pNext:=pCKey^.pNext;
pCKey^.pNext:=pAux
end;
Procedure DelComp(var sKey: Alfa; var pBegin: PComp);
begin
Find(sKey,pBegin,pCKey,pPreComp,bCond);
pPreComp^.pNext:=pCKey^.pNext
end;
begin
ClrScr;
writeln(' ÂÂÅÄÈ ÑÒÐÎÊÓ ');
readln(sC);
CreateLL(pBegin,pEnd,sC);
repeat
writeln('ÂÂÅÄÈ ÑÒÐÎÊÓ ');
readln(sC);
AddLL(pEnd,sC)
until sC='END';
writeln(' ***** ÂÛÂÎÄ ÈÑÕÎÄÍÎÃÎ ÑÏÈÑÊÀ *****');
pAux:=pBegin;
repeat
writeln(pAux^.sD);
pAux:=pAux^.pNext;
until pAux=NIL;
writeln;
writeln('ÂÂÅÄÈ ÊËÞ× ÄËß ÂÑÒÀÂÊÈ ÑÒÐÎÊÈ');
readln(sKey);
writeln('ÂÂÅÄÈ ÂÑÒÀÂËßÅÌÓÞ ÑÒÐÎÊÓ');
readln(sC);
InsComp(sKey,sC);
writeln;
writeln('ÂÂÅÄÈ ÊËÞ× ÓÄÀËßÅÌÎÉ ÑÒÐÎÊÈ');
readln(sKey);
DelComp(sKey,pBegin);
writeln;
writeln(' ***** ÂÛÂÎÄ ÈÇÌÅÍÅÍÍÎÃÎ ÑÏÈÑÊÀ *****');
pAux:=pBegin;
repeat
writeln(pAux^.sD);
pAux:=pAux^.pNext;
until pAux=NIL
end.
