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Thread: can someone solve this problem

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    Default can someone solve this problem

    Consider the sequence of digits from 1 through N (N<=9) in increasing order:
    1 2 3 4 N
    Insert either a + (for addition) or a - (for subtraction) between each of the digits so that the resultant sum is zero. Print all possible combinations that sum to zero.
    Example: Enter a number: 7
    1+2-3+4-5-6+7=0
    1+2-3-4+5+6-7=0
    1-2+3+4-5+6-7=0
    1-2-3-4-5+6+7=0


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    Default Re: can someone solve this problem

    What's preventing you from coding it yourself? No one here will do it for you, but we'll do our best to help you with your code. Post some, and ask specific questions about it if you're having trouble.

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    shilpy (September 3rd, 2014)

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    Default Re: can someone solve this problem

    i've tried a lot.....!!!!

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    Default Re: can someone solve this problem

    Do you have an algorithm for solving the problem? Maybe that needs some work before you try writing anymore code.
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: can someone solve this problem

    basically m unable to decode it ......we've to take combinations of all the numbers...that's fine but what to do with + or - signs arrangement.

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    Default Re: can someone solve this problem

    Without an algorithm its not possible to write any code.
    To start on an algorithm, take a short sequence like: 1,2,3 and make a list of all the possible expressions that work. Then move to the next longer sequence and do it again.
    What are the basic constraints?
    There must be at least 1 -
    The sum of the number of + and the number of - must equal the number of digits - 1.
    If you don't understand my answer, don't ignore it, ask a question.

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    shilpy (September 3rd, 2014)

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    Default Re: can someone solve this problem

    but how to put signs between them....how to decide....i am really very confused..!!!

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    Default Re: can someone solve this problem

    how to put signs between them
    For the String to disply, that will be done with String concatenation: "1" + "+" + "2" + "-" ....
    The algorithm needs to determine where the "+" and "-" go.

    When computing the sum, use -1 and +1 values:
    To change 4 to -4, multiply it by -1 => 4 * -1 = -4
    To leave 4 at 4, multiply it by +1 => 4 * +1 = 4

    Use the +1 and -1 values in various combinations to build the sum of the digits.
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: can someone solve this problem

    .....+ and - signs will also have permutation and combination sort of loop...to decide their positions..???

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    Default Re: can someone solve this problem

    Use arrays of +1 and -1 values to determine the signs to use.
    When building the String use "+" with a +1 value and "-" with the -1 value.
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: can someone solve this problem

    ...not to print in string...but for calculation part ...+ and - will be arranged in what manner....any sequence is used..?? please help me.. :/

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    Default Re: can someone solve this problem

    take a piece of paper and draw out all the possible patterns for some short sequences.
    Then find the logic to create all those patterns.

    For example with 3 digits the patterns might be:
    -+
    --
    +-
    If you don't understand my answer, don't ignore it, ask a question.

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    shilpy (September 4th, 2014)

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    Default Re: can someone solve this problem

    It may appear more familiar to you if you consider the possible permutations as binary patterns. In Norm's example, if - = 1 and + = 0, then the equivalent 0/1 binary patterns are:

    10
    11
    01

    and the missing one:

    00

    Good luck!

    Oops! Fixed my mixup.

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    shilpy (September 4th, 2014)

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    Default Re: can someone solve this problem

    ....so if i am getting right then i have to apply combinations in signs and a simple loop for numbers till the range entered ...!!! then i need not to apply "4* -1 = -4 " for making it negative...or positive...!!!

    --- Update ---

    ...i think now i can clearly solve it....!!! thanx sir...

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