How to iterate over a Golang map in sorted order

As a Golang map is an unordered collection, it does not preserve the order of keys. We can use additional data structures to iterate over these maps in sorted order.

Code

Let’s say we have a map of the first and last names of language designers. We want to print first and last names in sorted order by their first name.

We need to perform the following:

  1. Create a slice.
  2. Store keys to the slice.
  3. Sort the slice by keys.
  4. Iterate over the map by the sorted slice.
package main
import (
  "fmt"
  "sort"
)
func main() {
  designedBy := map[string]string {
    "Robert": "Griesemer",
    "Rob" : "Pike",
    "Ken": "Thompson",
  }
  // create slice and store keys
  firstNames := make([]string, 0, len(designedBy))
  for k := range designedBy {
	  firstNames = append(firstNames, k)
  }
  // sort the slice by keys
  sort.Strings(firstNames)
  // iterate by sorted keys
  for i, firstName := range firstNames {
    fmt.Println(i+1, firstName, designedBy[firstName])
  }
}

In Go version 1.12https://go.dev/doc/go1.12 and later, maps are printed in key-sorted order to ease testing.

Free AI Mock Interviews
Coding Interview
Coding PatternsFree Interview
Gain insights and practical experience with coding patterns through targeted MCQs and coding problems, designed to match and challenge your expertise level.
System Design
You TubeFree Interview
Learn to design a video streaming platform like YouTube by tackling functional and non-functional requirements, core components, and high-level to detailed design challenges.

Free Resources

License: Creative Commons-Attribution-ShareAlike 4.0 (CC-BY-SA 4.0)