O(len(a) + len(b))
is efficient. For example,
package main
import (
"fmt"
)
func main() {
a := []int{1, 2, 3, 4, 5}
b := []int{3, 4, 5, 6, 7, 8, 9}
fmt.Println(a)
fmt.Println(b)
m := make(map[int]uint8)
for _, k := range a {
m[k] |= (1 << 0)
}
for _, k := range b {
m[k] |= (1 << 1)
}
var inAAndB, inAButNotB, inBButNotA []int
for k, v := range m {
a := v&(1<<0) != 0
b := v&(1<<1) != 0
switch {
case a && b:
inAAndB = append(inAAndB, k)
case a && !b:
inAButNotB = append(inAButNotB, k)
case !a && b:
inBButNotA = append(inBButNotA, k)
}
}
fmt.Println(inAAndB)
fmt.Println(inAButNotB)
fmt.Println(inBButNotA)
}
Playground: https://play.golang.org/p/RvGaC9Wfjiv
Output:
[1 2 3 4 5]
[3 4 5 6 7 8 9]
[3 4 5]
[1 2]
[8 6 7 9]
The Go Programming Language Specification
& bitwise AND integers
| bitwise OR integers
^ bitwise XOR integers
&^ bit clear (AND NOT) integers
<< left shift integer << unsigned integer
>> right shift integer >> unsigned integer
We have 8 bits for uint8
. Bit 0 (1 << 0
, 1 shift left 0) is a
and bit 1 (1 << 1
; 1 shift left 1) is b
. For uint8
bits, 00000001
is a
, 00000010
is b
, 00000011
is a
and b
, and 00000000
is nether a
nor b
. The |
operator sets a bit, the &
operator reads a bit.
The Go Programming Language Specification
Map types
A map is an unordered group of elements of one type, called the
element type, indexed by a set of unique keys of another type, called
the key type.
The comparison operators == and != must be fully defined for operands
of the key type; thus the key type must not be a function, map, or
slice. If the key type is an interface type, these comparison
operators must be defined for the dynamic key values; failure will
cause a run-time panic.
The algorithm works for any slice type whose elements can be a map key. The comparison operators == and != must be fully defined for operands of the key type.