Problem 43. Subset Sum

Created by Cody Team

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Given a vector v of integers and an integer n, return the the indices of v (as a row vector in ascending order) that sum to n. If there is no subset in v that sums to n, return an empty matrix []. You can assume that the answer will always be unique.

Example:

 >> v = [2, 3, 5];
 >> n = 8;
 >> subset_sum(v, n)
 ans =
      2     3

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Last Solution submitted on May 09, 2025

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Sebastian on 2 Sep 2013

The combntns(eg.combntns(some_vector,i)) function throws:

Error: Undefined function 'combntns' for input arguments of type 'double'

But on my machine it takes i as a double. It even throws it if I cast i to int8.

Daniel Pereira on 8 May 2014

Use nchoosek instead of combnts or combnk

Thonigon on 8 Mar 2016

At first I thought that it was quite difficult to look for the sets of elements of any size (sets of 1 element, 2 elements and so on), but then I realised that any selection of the vector elements correspond to a binary code ('1' for selecting that element and '0' for not selecting it). To select all possible elements combinations I only need to use the binary code from 1 to 2^(1+length(v))-1.

Thonigon on 8 Mar 2016

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Problem 43. Subset Sum

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Problem 43. Subset Sum

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Problem Recent Solvers1953

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