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Thread: Java algorithm to print all the combination of the integer array

  1. #1
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    Default Java algorithm to print all the combination of the integer array

    Hi,

    I have an integer array and i want to print all the combinations of this integer array. can you please suggest me the algorithm?

    e.g int n[] ={1,2,3}
    and its combinations are 123,132,231,213,312,321

    problem is that i want the general algorithm which is independent of the array size.


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: Java algorithm to print all the combination of the integer array

    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: Java algorithm to print all the combination of the integer array

    Hi ,

    I try and find the algorithm but its acutal combinations are less than expectation.
    e.g if i have 6 number then my code gives 126 combinations .
    i try other algorithm but it repeats the combinations
    so please suggest the link for algorithm for this ........

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    Default Re: Java algorithm to print all the combination of the integer array

    Would this do it:
    Use all digits one at a time in first position
    use remaining digits one at a time in next position
    etc until no digits left
    If you don't understand my answer, don't ignore it, ask a question.

  5. The Following User Says Thank You to Norm For This Useful Post:

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    Default Re: Java algorithm to print all the combination of the integer array

    I donot understand.....

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    Default Re: Java algorithm to print all the combination of the integer array

    I think you are asking for:
    number of permutations of n distinct objects is n(n − 1)(n − 2)⋯21, which is commonly denoted as "n factorial" and written "n!".
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: Java algorithm to print all the combination of the integer array

    Hi,

    Yes, is there any algorithm for it..

  9. #8
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    Default Re: Java algorithm to print all the combination of the integer array

    What did google say? It usually has algorithms for common problems like this one.
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: Java algorithm to print all the combination of the integer array

    hi,

    i found some algorithm but they miss some combinations...

    is there any algorithm that print all the combinations and exactly once?

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    Default Re: Java algorithm to print all the combination of the integer array

    Sounds like you'll have to write the algorithm yourself. Take some time and think about it. If you run into road blocks come ask for help. I could just write the algorithm and give it to you, but that wont help you learn, you need to give it a shot.
    Writing code is your job, helping you fix and understand it is mine.

    <-- Be sure to thank and REP (Star icon) those who have helped you. They appreciate it!

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    Default Re: Java algorithm to print all the combination of the integer array

    Are you searching for combinations or permutations?
    This looks like permutations: 123,132,231,213,312,321

    What code have you tried?
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: Java algorithm to print all the combination of the integer array

    It seems as if it is a matter of the length of the array. Ignoring the possibility of two of the same number in the array, this should work:

    public int combinations(int length){
    		if(length == 1){
    			return 1;
    		}
    		else{
    			return length*combinations(length-1);
    		}
    	}

    The parameter for this method can be the length of the array. For example, n.length

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