Priority queue: Difference between revisions

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=={{header|XPL0}}==

The highest priority item is the one with the minimum number, as in 1st priority.

<syntaxhighlight lang "XPL0">def PQSize = 10; \Maximum number of items priority queue can hold

int PQ(PQSize*2), PQI;

func Remove; \Remove and return item with highest priority

int Min, I, MinI, Item;

[if PQI <= 0 then return 0;

Min:= -1>>1; I:= PQI;

while I > 0 do

[I:= I-2;

if PQ(I) < Min then

[Min:= PQ(I);

MinI:= I;

];

];

Item:= PQ(MinI+1); \get highest priority Item

PQI:= PQI-2;

PQ(MinI):= PQ(PQI); \replace that Item with last item

PQ(MinI+1):= PQ(PQI+1);

return Item;

];

proc Insert(Priority, Item); \Insert item into priority queue

int Priority, Item;

[if PQI >= PQSize*2 then return;

PQ(PQI):= Priority;

PQ(PQI+1):= Item;

PQI:= PQI+2;

];

int Items, I;

[Items:= [

[3, "Clear drains"],

[4, "Feed cat"],

[5, "Make tea"],

[1, "Solve RC tasks"],

[2, "Tax return"] ];

PQI:= 0;

for I:= 0 to 5-1 do

Insert(Items(I,0), Items(I,1));

for I:= 0 to 5-1 do

[Text(0, Remove); CrLf(0)];

]</syntaxhighlight>

{{out}}

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Solve RC tasks

Tax return

Clear drains

Feed cat

Make tea