Page: Sum of Subsests

Write and explain sum of subset algorithm for n = 5, W = {2, 7, 8, 9, 15} M = 17

  1. Given positive numbers (weight) w_i where (1<=i<=n) and m.

  2. This problem calls for finding all subsets of w_i whose sum is m.

  3. For e.g. if n=4, m=31, (w_1,w_2,w_3,w_4) = (11, 13, 24, 7).

  4. Then the desired subset are (11, 13, 7) and (2, 4, 7).

  5. In this method of giving the solution, the solution vector is given as variable-sized tuple (tuple is collection of element).

  6. The solution may also be expressed as fixed size tuple (x_1,x_(2,),x_3,…….,x_n) such that x_i =0 if w_i is not selected

x_i =1 if w_i is selected

  1. Using this strategy the solution would be (1,1,0,1) and (0,0,1,1)


  • Let n be the number of elements and let m be the required sum.

  • Let w[1…..n] be an array of weights in ascending order and Let x[1….n] be the solution vector.

  • Method

  • S → existing sum

  • w[k] → weight of current element

  • w[k+1] → weight of next element

  • s+w[k]+w[k+1]<=m → sum of existing element+weight of current element+weight of next element is less tham m.

  • Thus the next element can be selected for time being

  • s+r-w[k]>=m → Even if u discard the current element, you may still get the required sum later on.

  • s+w[k+1]<=m → The sum of selected element + weight of next element is less than m . This is even if u take the next element the sum will not exit the required sum(m)

  • Thus next element can be selected.


n = 5, W = {2, 7, 8, 9, 15} M = 17

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Hence, there are three subset with given sum m=17




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written 9 weeks ago by gravatar for stanzaa37 stanzaa3710
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