Simple golang RangeMap implementation for sorted, not overlapping ranges of integers (like IP address ranges). Elements are found using binary search.

rangemap.go

package main

import (
	"fmt"
	"sort"
)

type Range struct {
	L int
	U int
}

type RangeMap struct {
	Keys []Range
	Values []string
}
// works like Guava RangeMap com.google.common.collect.ImmutableRangeMap
// https://github.com/google/guava/blob/1efc5ce983c02cfaa2ce3338bdfaa1f583b66128/guava/src/com/google/common/collect/ImmutableRangeMap.java#L159
func (rm RangeMap) Get(key int) (string, bool) {
	i := sort.Search(len(rm.Keys), func(i int) bool {
		fmt.Printf("search %v at index %d for %v is %v\n", rm.Keys[i], i, key, key < rm.Keys[i].L)
		return key < rm.Keys[i].L
	})

	i -= 1
	if i >= 0 && i < len(rm.Keys) && key <= rm.Keys[i].U {
		return rm.Values[i], true
	}
	return "", false
}

func main() {
	rangeMap := RangeMap{ []Range{Range{1,2}, Range{3,4}, Range{6,8}, Range{12,16}, Range{17,18}},
		[]string{"a","b","c","d","e"} }

	x := 14
	value, ok := rangeMap.Get(x)
	fmt.Printf("found %v '%s' for %d\n", ok, value, x)
	x = 5
	value, ok = rangeMap.Get(x)
	fmt.Printf("found %v '%s' for %d\n", ok, value, x)
}

// search {6 8} at index 2 for 14 is false
// search {17 18} at index 4 for 14 is true
// search {12 16} at index 3 for 14 is false
// found true 'd' for 14
// search {6 8} at index 2 for 5 is true
// search {3 4} at index 1 for 5 is false
// found false '' for 5