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Thread: PriorityQueue Enquiries

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    Default PriorityQueue Enquiries

    Hi All,

    I try to google around for how can i do the following thing in priorityqueue but there is no answer for this.

    It is actually quite straight forward, lets said i have a set of PriorityQueue with few items inside and I want to get the object n in the pq and do a comparison, if the path is higher cost, replace with a new object n. The Pseudo code is something like this.

    If Child.STATE is in PriorityQueue with Higer PATH-COST then
    replace that PriorityQueue with the Child.STATE

    Anyone able to guide me on this? Coz i believe PriorityQueue does not have the GET function.

    Cheers.


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: PriorityQueue Enquiries

    Would contains and remove do what you want?

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    Default Re: PriorityQueue Enquiries

    Quote Originally Posted by Norm View Post
    Would contains and remove do what you want?
    I would like to get the Object N from the priority Queue and do a comparison with current object .. if current object contains lesser cost-path, it will replace the object N..

    2 Object would have same attribute different path cost ...

    Is it more like a travel using UCS ..

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    Default Re: PriorityQueue Enquiries

    Can you write a small simple program that compiles and executes to show what you want to do?

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    Default Re: PriorityQueue Enquiries

    Quote Originally Posted by Norm View Post
    Can you write a small simple program that compiles and executes to show what you want to do?
    My program is something like this.

    I have an input files as follow

    5 5
    1 1
    5 5

    1 1 1 1 1
    1 1 1 1 1
    1 1 1 1 1
    1 1 1 1 1

    5 5 = indicates Grid Size
    1 1 = indicates Start Location
    5 5 = indicates Goal Location
    The travel path will be replaced by *

    The real answer should be

    * 1 1 1 1
    * 1 1 2 1
    * 1 3 1 1
    * 1 1 1 1
    * * * * *

    It would use priority queue to compare if terrain level is higher or same level using the following formula.

    If Node(c,d) - Node(a,b) > 0 then
    Path Cost = 1 + Node(c,d)[Terrain Level] - Node(a,b)[Terrain Level] + Parent Path Cost

    The start goal will have 0 path cost.

    It should travel by 4 direction in sequence, Up - Down - Left - Right

    My output files as follow:-

    * * * * *
    1 1 1 2 *
    1 1 3 1 *
    1 1 1 1 *
    1 1 1 1 *

    So, what i suspect my program wrong is because i do not compare the path cost which contain the node.

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    Default Re: PriorityQueue Enquiries

    sorry I meant a java program that compiles and executes to show what you want to do. You know, with classes and methods that execute.

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    Default Re: PriorityQueue Enquiries

    Quote Originally Posted by keat84 View Post
    I would like to get the Object N from the priority Queue
    A queue is a queue - get(int) works on a list. If you want to get the nth item based on a 'cost' you'll have to use Collections.sort on a list (or Arrays.sort on an array) and pass it a Comparator that uses your cost calculation (if it's not already your object's natural order).

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