Go - Sorting Maps

Problem: You want to sort a map by its keys.

Solution: Get the keys of the map in a slice and sort that slice. Then, using the sorted slice of keys, iterate through the map again.

 

Maps are unordered. This means each time you iterate through a map, the order of the key-value pairs might not be the same as the previous time. So how can you ensure that it’s the same each time?

First, extract the keys into a slice:

func main() {
    people := map[string]int{
        "Alice": 22,
        "Bob": 18,
        "Charlie": 23,
        "Dave": 27,
        "Eve": 31,
    }

    var keys []string
    for k := range people {
        keys = append(keys, k)
    }
}

Then sort the keys accordingly. In this case, you want to sort by descending order:

    sort.Strings(keys)
    for i := len(keys)/2 - 1; i >= 0; i-- {
        opp := len(keys) - 1 - i
        keys[i], keys[opp] = keys[opp], keys[i]
    }

Finally, you can access the map by the descending order of the keys:

    for _, key := range keys {
        fmt.Println(key, people[key])
    }