在HashMap中进行部分搜索 [英] Partial search in HashMap

问题描述

我需要创建电话簿的东西。它包含名称&数。现在当我输入字母匹配列表应该被返回。对于下面给出的示例，当我输入H时，应该返回包含Harmer，Harris，Hawken，Hosler的列表。当哈哈然后列表只包含哈默尔，哈里斯，霍肯应该归还。

I need to create phone book kind of thing. It contains name & number. Now when I type letters matching list should be returned. For the example given below, when I type H, a list containing Harmer, Harris, Hawken, Hosler should be returned. When type Ha then list containing only Harmer, Harris, Hawken should be returned.

  Map<String, String> nameNum = new HashMap<String, String>();

  nameNum.put("Brown", "[phone]");
  nameNum.put("Bob", "[phone]");
  nameNum.put("Harmer", "[phone]");
  nameNum.put("Harris", "[phone]");
  nameNum.put("Hawken", "[phone]");
  nameNum.put("Hosler", "[phone]");

任何想法如何实现？
提前感谢。

Any idea how achieve it? Thanks in advance.

推荐答案

是的，HashMap不是正确的数据结构。正如Bozho所说， Trie 将是正确的。

Yeah, a HashMap is not the right data structure for this. As Bozho said, a Trie would be the right one.

使用Java的板载工具，TreeMap（或任何 SortedMap ，实际上）可以使用：

With Java's on-board tools, a TreeMap (or any SortedMap, actually) could be used:

public <V> SortedMap<String, V> filterPrefix(SortedMap<String,V> baseMap, String prefix) {
    if(prefix.length() > 0) {
        char nextLetter = prefix.charAt(prefix.length() -1) + 1;
        String end = prefix.substring(0, prefix.length()-1) + nextLetter;
        return baseMap.subMap(prefix, end);
    }
    return baseMap;
}

输出甚至会按键排序。

这里有一个用法示例：

SortedMap<String, String> nameNum = new TreeMap<String, String>();
// put your phone numbers

String prefix = ...;
for(Map.Entry<String,String> entry : filterPrefix(nameNum, prefix).entrySet()) {
    System.out.println(entry);
}

如果您希望前缀过滤器不取决于案例差异，请使用适合您的地图的比较器（如 Collat​​or ，具有合适的强度设置，或 String.CASE_INSENSITIVE_ORDER ）

If you want your prefix filter to not be depending on case differences, use a suitable Comparator for your map (like a Collator with a suitable strength setting, or String.CASE_INSENSITIVE_ORDER).

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