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我在Java中实现了Trie数据结构,但在运行代码时没有得到正确的答案。我使用一些简单的字符串构建了trie。然后我搜索单词和前缀,但结果不正确。我试过很多次,但仍然找不到可能出错的地方。在Java中实现Trie
Trie.java:
public class Trie {
public class Vertex {
public int words;
public int prefixes;
public Vertex edges[] = new Vertex[26];
public Vertex() {
this.words = 0;
this.prefixes = 0;
}
}
private Vertex root;
Trie() {
this.root = new Vertex();
}
private void addWord(Vertex vertex, String word) {
if (word.isEmpty()) {
vertex.words++;
} else {
vertex.prefixes++;
int indexOfNextChar = (int) word.charAt(0) - 97;
vertex.edges[indexOfNextChar] = new Vertex();
this.addWord(vertex.edges[indexOfNextChar], word.substring(1));
}
}
private int countWords(Vertex vertex, String word) {
if (!word.isEmpty()) {
int indexOfNextChar = (int) word.charAt(0) - 97;
if (vertex.edges[indexOfNextChar] == null) {
return 0;
} else {
return this.countWords(vertex.edges[indexOfNextChar], word.substring(1));
}
} else {
return vertex.words;
}
}
private int countPrefixes(Vertex vertex, String word) {
if (!word.isEmpty()) {
int indexOfNextChar = (int) word.charAt(0) - 97;
if (vertex.edges[indexOfNextChar] == null) {
return 0;
} else {
return this.countPrefixes(vertex.edges[indexOfNextChar], word.substring(1));
}
} else {
return vertex.prefixes;
}
}
public void addWord(String word) {
this.addWord(this.root, word.toLowerCase());
}
public int countPrefixes(String word) {
if (word.length() != 0) {
return this.countPrefixes(this.root, word.toLowerCase());
}
return -1;
}
public int countWords(String word) {
if (word.length() != 0) {
return this.countWords(this.root, word.toLowerCase());
}
return -1;
}
}
TrieTester.java
public class TrieTester {
public static void main(String[] args) {
Trie trie = new Trie();
trie.addWord("Ayush");
trie.addWord("Ayur");
trie.addWord("Ayub");
trie.addWord("Ayan");
trie.addWord("Bhushan");
// Should output 0, outputs 0
System.out.println("Count of word Ayus: " + trie.countWords("Ayus"));
// Should output 1, outputs 0
System.out.println("Count of word Ayush: " + trie.countWords("Ayush"));
// Should output 4, outputs 1
System.err.println("Count of prefix Ay: " + trie.countPrefixes("Ay"));
}
}
我提到的Topcoder Trie tutorial来实现这一点。
我开始测试1字符的字符串,然后是2个字符的字符串,并检查trie的完整状态。 – 9000
使用调试器逐步完成,并仔细观察边缘情况。尤其要注意当你创建一个新的顶点时,你需要在创建第一个顶点之后重用它们。 –