Data structures that can map a range of keys to a value

Question

I am trying to find a data structure that takes in a particular value from a range of values and map it to a key.

For example, I have the following conditions:

Answer 1

Are your ranges non-overlapping? If so you could use a TreeMap:

TreeMap m = new TreeMap();
m.put(1.0, 'A');
m.put(2.9, null);
m.put(4.0, 'B');
m.put(6.0, null);
m.put(6.5, 'C');
m.put(10.0, null);

The lookup logic is a bit complicated by the fact that you probably want an inclusive lookup (i.e. 2.9 maps to 'A', and not undefined):

private static  V mappedValue(TreeMap map, K key) {
    Entry e = map.floorEntry(key);
    if (e != null && e.getValue() == null) {
        e = map.lowerEntry(key);
    }
    return e == null ? null : e.getValue();
}

Example:

mappedValue(m, 5) == 'B'

More results include:

0.9 null
1.0 A
1.1 A
2.8 A
2.9 A
3.0 null
6.4 null
6.5 C
6.6 C
9.9 C
10.0 C
10.1 null