可以将一系列值映射到键的数据结构？ [英] Data structures that can map a range of values to a key?

问题描述

我正在尝试找到一个数据结构，从一系列值获取特定的值，并将其映射到一个键。

例如，我有以下条件：

1. 从1到2.9，我想将其映射到A。


2. 从4到6，我想把它映射到B。


3. 从6.5到10，我想把它映射到C。

我的值为5，我想将其映射到一个键。所以基于上述条件，我应该将其映射到B。

Java中有没有任何人可以推荐我来解决问题的数据结构？ >

目前，我正在使用只能将值映射到键的哈希表。我尝试将值的范围映射到哈希表中存在的特定值。但是，我将值范围映射到一个特定的值。所以现在我试图做另一种方法来将值的范围映射到一个键。有没有人有任何想法如何解决这个问题？

编辑：

感谢Martin Ellis，决定使用TreeMap来解决问题。

解决方案

你的范围是不重叠的吗？如果是，您可以使用TreeMap：

  TreeMap< Double，Character> m = new TreeMap< Double，Character>（）; 
 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）; 
  

查找逻辑有点复杂，你可能想要一个包容性查找（即2.9地图到'A'，而不是未定义）：

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

示例：

  mappedValue（m，5）=='B'
  

更多结果包括：

  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 
  

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:

1. From 1 to 2.9, I want to map it to A.
2. From 4 to 6, I want to map it to B.
3. From 6.5 to 10, I want to map it to C.

I have a value of 5 and I would like to map it to a key. So based on the above conditions, I should map it to B.

Is there any data structure in Java that anyone can recommend to me to solve the problem?

Currently I am using a hashtable that can only map a value to a key. I tried to map the range of values to a particular value that exists in the hashtable. However, I got stuck in the mapping of the range of values to a particular value. So now I am trying to do another way of mapping the ranges of values to a key. Does anyone have any idea how I can solve this problem?

EDIT:

Thanks to Martin Ellis, I decided to use TreeMap to solve the problem.

解决方案

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

TreeMap<Double, Character> m = new TreeMap<Double, Character>();
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 <K, V> V mappedValue(TreeMap<K, V> map, K key) {
    Entry<K, V> 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

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