zsort

README

Package zsort provides useful additions to the sort package

Super early stage, not for production use yet!

Documentation

Index

• func Partial[S ~[]E, E cmp.Ordered](x S, n int)
• func PartialFunc[S ~[]E, E any](x S, n int, less func(E, E) bool)
• func Partition[S ~[]E, E any](x S, pred func(int) bool) int

Examples

• Partial
• PartialFunc
• Partition

Functions

func Partial

func Partial[S ~[]E, E cmp.Ordered](x S, n int)

Partial sorts the first n elements of x, such that they are the smallest n elements in ascending order, using the type's natural ordering. The remaining elements in the slice are not sorted but are guaranteed to be greater than or equal to the elements in the first n positions.

x is sorted in-place. The sort is not guaranteed to be stable: equal elements may be reversed from their original order

Example

package main

import (
	"fmt"

	"github.com/arl/zsort"
)

func main() {
	s := []int{5, 2, 6, 3, 1, 4, 0, 9, 8, 7}

	zsort.Partial(s, 3)

	fmt.Println(s[:3])
}

Output:

[0 1 2]

func PartialFunc

func PartialFunc[S ~[]E, E any](x S, n int, less func(E, E) bool)

PartialFunc sorts the first n elements of x, such that they are the smallest n elements, given the provided less function. The remaining elements in the slice are not sorted but are guaranteed to be greater than or equal to the elements in the first n positions.

x is sorted in-place. The sort is not guaranteed to be stable: equal elements may be reversed from their original order

Example

package main

import (
	"fmt"

	"github.com/arl/zsort"
)

func main() {
	type person struct {
		name string
		age  int
	}

	persons := []person{
		{"Alice", 19},
		{"Bob", 17},
		{"Jane", 36},
		{"Henri", 24},
		{"Sandra", 22},
	}

	zsort.PartialFunc(persons, 3, func(p1, p2 person) bool { return p1.age > p2.age })

	fmt.Println(persons[:3])
}

Output:

[{Jane 36} {Henri 24} {Sandra 22}]

func Partition

func Partition[S ~[]E, E any](x S, pred func(int) bool) int

Partition rearranges the elements of x so that all elements for which pred returns true are placed before all elements for which pred returns false. There is no guarantee about the order of the elements within each partition. Partition returns the index of the first element in the second partition.

Note that the predicate receives the index of the element in the slice, not the element itself.

Example

package main

import (
	"fmt"

	"github.com/arl/zsort"
)

func main() {
	s := []int{7, 1, 1, 7, 1, 1, 7}

	split := zsort.Partition(s, func(i int) bool { return s[i] >= 3 })

	fmt.Println("split =", split)
	fmt.Println(s)

}

Output:

split = 3
[7 7 7 1 1 1 1]