## Amazon interview question Comment hidden because of low score. Click to expand.
1
of 1 vote

Get all sub-sets of the questions set [which can be can have as many as (2^sizeOfSet)-1 elements].

int maxNumOfSubsets = (2^set.size())-1
Getting all sub-sets can be done by using the binary representation of all integers between 1 and maxNumOfSubsets.

The simply sum each sub-set, if the sum is zero then you have an answer.

``````private static String binary(int numOfBits, int value) {
StringBuilder builder = new StringBuilder();
while (numOfBits>0) {
int a = value % 2;
if (a>0) builder.append("1");
else builder.append("0");
value /= 2;
numOfBits--;
}
return builder.toString();
}

private static List<Set<Integer>> subsets(int[] array) {
List<Set<Integer>> result = new LinkedList<Set<Integer>>();
int size = array.length;
int max = (int) ((Math.pow(2, size)) - 1);
List<String> binaryValues = new LinkedList<String>();
for (int i = 1; i<=max; i++) {
String binary = binary(size, i);
binaryValues.add(binary);
}
for (String s : binaryValues) {
Set<Integer> set = new HashSet<Integer>();
for (int i=0; i<s.length(); i++) {
if (s.charAt(i)=='1')
set.add(array[i]);
}
result.add(set);
}
return result;
}

private static int sum(Set<Integer> set) {
int result = 0;
for (int i : set) {
result += i;
}
return result;
}

private static List<Set<Integer>> solve(int[] array) {
List<Set<Integer>> subsets = subsets(array);
List<Set<Integer>> list = new LinkedList<Set<Integer>>();
for (Set<Integer> s : subsets) {
int sum = sum(s);
if (sum==0)
list.add(s);
}
return list;
}``````

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