Sorting and Searching with Go's `sort` Package

In this article, we will explore how to use Go's built-in sort package to perform sorting and searching operations efficiently. The sort package provides functions to sort slices and user-defined collections by implementing the sort.Interface.

Sorting Slices

The sort package provides the following functions to sort slices of basic types:

• sort.Ints(slice []int) - sorts a slice of integers in increasing order.
• sort.Strings(slice []string) - sorts a slice of strings in increasing order (lexicographical order).
• sort.Float64s(slice []float64) - sorts a slice of float64 in increasing order.

Let's see how these work with examples.

package main

import (
    "fmt"
    "sort"
)

func main() {
    // Sorting an integer slice
    intSlice := []int{7, 2, 9, 4, 1}
    sort.Ints(intSlice)
    fmt.Println("Sorted integer slice:", intSlice)

    // Sorting a string slice
    stringSlice := []string{"banana", "apple", "pear", "kiwi"}
    sort.Strings(stringSlice)
    fmt.Println("Sorted string slice:", stringSlice)

    // Sorting a float64 slice
    floatSlice := []float64{2.3, 1.4, 3.9, 0.7}
    sort.Float64s(floatSlice)
    fmt.Println("Sorted float64 slice:", floatSlice)
}

Custom Sort Using sort.Interface

For more complex sorting, such as sorting a slice of structs, you need to implement the sort.Interface which consists of the following three methods:

• Len() - returns the length of the collection.
• Less(i, j int) bool - reports whether the element at index i should sort before the element at index j.
• Swap(i, j int) - swaps the elements with indexes i and j.

Here's an example of a custom sort by implementing the sort.Interface to sort a slice of structs.

package main

import (
    "fmt"
    "sort"
)

type Person struct {
    Name string
    Age  int
}

// ByAge implements sort.Interface for []Person based on the Age field.
type ByAge []Person

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() {
    people := []Person{{"Alice", 30}, {"Bob", 25}, {"Charlie", 35}}
    sort.Sort(ByAge(people))
    fmt.Println("Sorted by Age:", people)
}