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# can anybody explain the meaning of this programming problem please

Ranch Hand
Posts: 817
Hi,
can anybody explain the meaning of this programming problem please
Thanks

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Problem Statement
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You are given a set of two-dimensional vectors in two int[]s - x and y (the i-th elements of x and y represent x and y coordinates of the i-th vector). Find a subset of the vectors such that the sum of all vectors in the subset has the maximum possible length. Return this length.
Definition
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Class:
VectorSet
Method:
maxLength
Parameters:
int[], int[]
Returns:
double
Method signature:
double maxLength(int[] x, int[] y)
(be sure your method is public)
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Notes
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The sum of vectors (x1, y1) and (x2, y2) is the vector (x1+x2, y1+y2).
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The length of vector (x, y) is the value sqrt(x * x + y * y).
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The returned value must be accurate to within a relative or absolute value of 1E-9.
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The input (as well as the resulting subset) can contain equal vectors (see example 1).
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Consider the entire set to be a subset.
Constraints
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x will contain between 1 and 50 elements, inclusive.
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x and y will contain the same number of elements.
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Each element of x will be between -1000 and 1000, inclusive.
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Each element of y will be between -1000 and 1000, inclusive.
Examples
0)

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{0,0}
{1,-1}
Returns: 1.0
Choose any one vector.
1)

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{0, 0}
{1, 1}
Returns: 2.0
Choose two vectors. The sum is (0, 2).
2)

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{0, 0, 1, -1}
{1, -1, 0, 0}
Returns: 1.4142135623730951

3)

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{0, 0, 0, 0}
{1, 2, -1, -2}
Returns: 3.0

4)

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{17,8,-5,-8,-8,-11,-3,2,19,4,22,15,20,13,-7,15,-23,17,-9,-10,17,24,20,-22,-1,-7,-19,18,-17}
{7,-5,-2,18,-9,-24,14,9,-21,14,-23,7,14,23,23,17,17,22,-3,-21,-10,1,24,-17,25,12,-21,12,13}
Returns: 289.4563870430224

Rancher
Posts: 13459
Moving to the Java in General (beginner) forum.

To anybody that decides to help:
Please try to be as helpful as possible without providing complete solutions. In the long run these don't help anyone

Dave

Greenhorn
Posts: 16
Here is a hint:

Brute force: Compute the length of all possibilities and choose the highest length.
You can do this recursively, by making a method that calls itself n (=arraylength) times each time removing one element from the arrays.
That way, you get n! (n * n-1 * n-2 * ... * 2 * 1) iterations.

 It is sorta covered in the JavaRanch Style Guide.