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我正在使用尝试数据结构来根据数字前缀来确定语音号码属于哪个国家。在Java中修改尝试代码
我使用的弗拉基米尔Kroz创造了尝试次数的实现，它的作品真的很好：here
这是我如何填充尝试次数图：
private static Trie<Country> trie = new Trie<>();
trie.put("7", new Country(countryID, country));
trie.put("794", new Country(countryID, country));
正如你所看到的尝试次数保存电话号码前缀键和国家对象作为价值。
这是我如何执行搜索：
Country country = trie.get("79519637944");
String CountryName = country.getName();
正如你可以看到我使用一个电话号码为关键字。现在尝试尝试为此号码找到匹配的前缀。尝试将尽可能从第一个数字开始抓取。如果它在树中找不到任何匹配的数字，那么它将返回该特定前缀的值。
它工作得很好，但需要稍微调整一下。
比方说，我有前缀7和前缀746
现在，当我试图找到电话NR 74568706987069，然后尝试将返回null，因为它会爬到树这样7-> 4->将尝试找到5，但它不会返回与前缀74相关的值而不是7.
如何使它记住最后一个前缀的值不为空。
尝试次数代码如下（搜索发生在_GET方法的地方）：
import java.util.HashMap;
import java.util.Map;
/**
* Prefix table based on trie structure. Allows to perform incremental lookup
* and match based on search key prefixes (classic example - determine phone
* area code for given phone number)
*
* @param <V>
* a type of value object to be stored along with prefix (e.g when
* key is a country name, the value could be a name of the country)
*
* @author Vladimir Kroz
*/
public class Trie<V> {
Entry<V> entry;
char key;
Map<Character, Trie<V>> childrens;
public Trie() {
this.childrens = new HashMap<Character, Trie<V>>(10);
entry = new Entry<V>();
}
/** non-public, used by _put() */
Trie(char key) {
this.childrens = new HashMap<Character, Trie<V>>(10);
this.key = key;
entry = new Entry<V>();
}
public void put(String key, V value) {
_put(new StringBuffer(key), new StringBuffer(""), value);
}
void _put(StringBuffer remainder, StringBuffer prefix, V value) {
if (remainder.length() > 0) {
char keyElement = remainder.charAt(0);
Trie<V> t = null;
try {
t = childrens.get(keyElement);
} catch (IndexOutOfBoundsException e) {
}
if (t == null) {
t = new Trie<V>(keyElement);
childrens.put(keyElement, t);
}
prefix.append(remainder.charAt(0));
t._put(remainder.deleteCharAt(0), prefix, value);
} else {
this.entry.value = value;
this.entry.prefix = prefix.toString();
}
}
/**
* Retrieves element from prefix table matching as a prefix to provided key.
* E.g. is key is "abcde" and prefix table has node "ab" then this call will
* return "ab"
*
* @param key
* a string which starts with prefix to be searched in the table
* (e.g. phone number)
* @return an Object assosiated with matching prefix (i.e if key is a phone
* number it may return a corresponding country name)
*/
public V get(String key) {
return _get(new StringBuffer(key), 0);
}
/**
* Returns true if key has matching prefix in the table
*/
public boolean hasPrefix(String key) {
return ((this.get(key) != null) ? true : false);
}
V _get(StringBuffer key, int level) {
if (key.length() > 0) {
Trie<V> t = childrens.get(key.charAt(0));
if (t != null) {
return t._get(key.deleteCharAt(0), ++level);
} else {
return (level > 0) ? entry.value : null;
}
} else {
return entry.value;
}
}
@Override
public String toString() {
return "Trie [entry=" + entry + ", key=" + key + ", childrens="
+ childrens + "]";
}
static public class Entry<V> {
String prefix;
V value;
public Entry() {
}
public Entry(String p, V v) {
prefix = p;
value = v;
}
public String prefix() {
return prefix;
}
public V value() {
return value;
}
@Override
public String toString() {
return "Entry [prefix=" + prefix + ", value=" + value + "]";
}
}
}
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