Sorting in Golang
Golang’s sort package implements sorting for builtins and user-defined types. There are 3 different ways to sort a slice in golang depending on the data stored in the slice.
Sort builtins types like int, float and string
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package main import ( "fmt" "sort" ) func main() { //sort slice containing strings strs := []string{"New York", "London", "Seattle"} sort.Strings(strs) fmt.Println("Strings:", strs) //sort slice containing ints ints := []int{17, 2, 14, 1, 5} sort.Ints(ints) fmt.Println("Ints: ", ints) //sort slice containing floats floats := []float64{23.93, 2.3, 2.5, 5.2} sort.Float64s(floats) fmt.Println("Floats: ", floats) } |
Output
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Strings: [London New York Seattle] Ints: [1 2 5 14 17] Floats: [2.3 2.5 5.2 23.93] |
Sort Custom Data Structures
Sometimes our collection holds custom data structures, we have to sort the collection depends on particular condition. Golang provides feature to sort custom data structures as well.
To sort custom data structures, type should implements interface below
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type Interface interface { // Len is the number of elements in the collection. Len() int // Less reports whether the element with // index i should sort before the element with index j. Less(i, j int) bool // Swap swaps the elements with indexes i and j. Swap(i, j int) } |
Program to sort custom data structures.
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package main import ( "fmt" "sort" ) type Emp struct { FirstName string LastName string Age int } type ByAge []Emp func (a ByAge) Len() int { return len(a) } func (a ByAge) Less(i, j int) bool { return a[i].Age < a[j].Age } func (a ByAge) Swap(i, j int) { a[i], a[j] = a[j], a[i] } func main() { emps := []Emp{ {"Rahul", "Anand", 29}, {"C", "Anderson" , 20}, {"Bob", "Anderson", 25}, } sort.Sort(ByAge(emps)) fmt.Println(emps) } |
Output
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[{C Anderson 20} {Bob Anderson 25} {Rahul Anand 29}] |
Sort using anonymous function (Custom Comparator)
Prior to Go 1.8, there is an easier way to sort a slice that does not require to define new types. You simply pass an anonymous function to the sort.Slice function
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package main import ( "fmt" "sort" ) func main() { emps := []struct { FirstName string LastName string Age int }{ {"Rahul", "Anand", 29}, {"C", "Anderson" , 20}, {"Bob", "Anderson", 25}, } sort.Slice(emps, func(i, j int) bool { return emps[i].Age < emps[j].Age }) fmt.Println(emps) } |
Output
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[{C Anderson 20} {Bob Anderson 25} {Rahul Anand 29}] |
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