priority-queue functions

gregg.irwin (Gregg Irwin) — Fri, 13 Jan 2006 04:00:13 GMT


REBOL [

    Title: "Cheasy (Cheap-n-Easy) Priority Queue"

]



pq-insert: func [

    list [any-block!]   "The queue"

    item

    priority [integer!]

][

    sort/skip/reverse append list reduce [priority item] 2

]



pq-remove: func [

    "Remove an item from the priority queue"

    list [any-block!]   "The queue"

    /index  "Remove a specific item"

        idx [integer!] "The specific item to remove"

][

    remove/part either index [at list (idx * 2 - 1)][head list] 2

]



pq-first: func [

    list [any-block!]   "The queue"

][

    ; skip over the priority value and return the actual value

    ; that was inserted in the queue.

    first next head list

]



priority-queue: make object! [

    data: copy []



    insert: func [item priority] [pq-insert data item priority]



    remove: func [/index idx] [

        either index [pq-remove/index data idx][pq-remove data]

    ]



    first: does [pq-first data]

]







pq: copy []

print pq-insert pq "A" 1

print pq-insert pq "B" 10

print pq-insert pq "C" 100

print pq-insert pq "D" 1000

print pq-remove/index pq 3

print pq-remove pq

print mold pq

print pq-insert pq "CC" 100

print pq-insert pq "CCC" 100

print pq-insert pq "D" 1000

print pq-insert pq "CCCC" 100

print pq-insert pq "CCCCC" 100

print pq-remove pq

print pq-insert pq "CCCCCC" 100

print pq-insert pq "CCCCCCC" 100



print ""



pq: make priority-queue []

print pq/insert"A" 1

print pq/insert"B" 10

print pq/insert"C" 100

print pq/insert"D" 1000

print pq/remove/index 3

print pq/remove ;pq

print mold pq/data

print pq/insert"CC" 100

print pq/insert"CCC" 100

print pq/insert"D" 1000

print pq/insert"CCCC" 100

print pq/insert"CCCCC" 100

print pq/remove ;pq/data

print pq/insert"CCCCCC" 100

print pq/insert"CCCCCCC" 100





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DZone Snippets: priority code

priority-queue functions
