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/*
Title: 40.Sorting_By_Functions.go
Author: OpenSource
Date: 2017-05-22
Description: For Study
Sometimes we’ll want to sort a collection by something other than its natural order.
For example, suppose we wanted to sort strings by their length instead of alphabetically.
Here’s an example of custom sorts in Go.
*/
package main
import (
"sort"
"fmt"
)
// In order to sort by a custom function in Go, we need a corresponding type.
// Here we’ve created a ByLength type that is just an alias for the builtin []string type.
type ByLength []string
// We implement sort.Interface - Len, Less, and Swap -
// !!! So Len , Swap , Less function is absolutely needable function.
// !!! cause' sort.Sort(ByLength(aryStr)) is rquired them
// on our type so we can use the sort package’s generic Sort function.
// Len and Swap will usually be similar across types
// and Less will hold the actual custom sorting logic.
// In our case we want to sort in order of increasing string length,
// so we use len(s[i]) and len(s[j]) here.
func (s ByLength) Len() int{
return len(s)
}
func (s ByLength) Sawp(i, j int){
s[i], s[j] = s[j], s[i]
}
func (s ByLength) Less(i, j int) bool {
return len(s[i]) < len(s[j])
}
// With all of this in place,
// we can now implement our custom sort by casting the original fruits slice to ByLength,
// and then use sort.Sort on that typed slice.
func main(){
fmt.Println("40.Sorting_By_Functions.go---------Start------------\n\n")
fruits := []string{"peach", "banana", "kiwi"}
fmt.Println(fruits)
sort.Sort(ByLength(fruits))
fmt.Println(fruits)
fmt.Println("40.Sorting_By_Functions.go---------Start------------\n\n")
// Running our program shows a list sorted by string length, as desired.
// By following this same pattern of creating a custom type,
// implementing the three Interface methods on that type, and then calling sort.Sorting
// on a collection of that custom type, we can sort Go slices by arbitrary functions.
}
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