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[Set Operations]

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Tags: #set #theory #operations #go #golang

Set Operations.md

Union

The union of two sets is a set containing all elements that are in A or in B (possibly both). For example, {1,2}∪{2,3}={1,2,3}.

Intersection

The intersection of two sets A and B, denoted by A∩B, consists of all elements that are both in A and B. For example, {1,2}∩{2,3}={2}.

Difference

The difference (subtraction) is defined as follows. The set A−B consists of elements that are in A but not in B. For example if A={1,2,3} and B={3,5}, then A−B={1,2}.

Complement

The complement of a set A, denoted by Ac, is the set of all elements that are in the universal set S but are not in A.

Golang

It is easy to create a set from map:

s := map[int]bool{5: true, 2: true}

_, ok := s[6] // check for existence
s[8] = true   // add element 
delete(s, 2)  // remove element

Union

s_union := map[int]bool{}
for k, _ := range s1{
    s_union[k] = true
}
for k, _ := range s2{
    s_union[k] = true
}

Intersection

s_intersection := map[int]bool{}
for k,_ := range s1 { 
  if s2[k] {
    s_intersection[k] = true
  }
}