字典树

关于字典树的解释请看网址：http://www.java3z.com/cwbwebhome/article/article8/83591.html?id=4750

该网址贴出了java实现一个a-z 26个字母的字典树以及一个案例，一定要看这个案例。

</pre>下面是java代码：</p><p>public class Trie {<span style="white-space:pre">	</span><span style="white-space:pre">	</span>private class TrieNode{<span style="white-space:pre">	</span>//内部类，字典树节点类<span style="white-space:pre">		</span>private int num;<span style="white-space:pre">	</span>//有多少单词通过这个节点，即节点字符出现的次数，也说明了有多少son引用被用到，或者说有多少条被用到的树的边，或者说是该节点的度<span style="white-space:pre">		</span>private TrieNode[] son;<span style="white-space:pre">	</span>//所有儿子节点<span style="white-space:pre">		</span>private boolean isEnd;<span style="white-space:pre">	</span>//是不是最后一个节点<span style="white-space:pre">		</span>private char val;<span style="white-space:pre">	</span>//节点的值<span style="white-space:pre">		</span><span style="white-space:pre">		</span>TrieNode(){<span style="white-space:pre">			</span>num = 1;<span style="white-space:pre">			</span>son = new TrieNode[SIZE];<span style="white-space:pre">			</span>isEnd = false;<span style="white-space:pre">		</span>}<span style="white-space:pre">	</span>}<span style="white-space:pre">	</span><span style="white-space:pre">	</span>private int SIZE = 26;<span style="white-space:pre">	</span>private TrieNode root;<span style="white-space:pre">	</span>//字典树的根<span style="white-space:pre">	</span><span style="white-space:pre">	</span>Trie(){<span style="white-space:pre">		</span>root = new TrieNode();<span style="white-space:pre">	</span>}<span style="white-space:pre">	</span><span style="white-space:pre">	</span>//在字典树中插入一个单词<span style="white-space:pre">	</span>public void insert(String str){<span style="white-space:pre">	</span><span style="white-space:pre">		</span>if(str == null || str.length() == 0)<span style="white-space:pre">			</span>return;<span style="white-space:pre">		</span><span style="white-space:pre">		</span>TrieNode node = root;<span style="white-space:pre">		</span>char[] letters = str.toCharArray();<span style="white-space:pre">		</span>for(int i = 0, len = str.length(); i< len; i++){<span style="white-space:pre">			</span>int pos = letters[i] - 'a';<span style="white-space:pre">			</span>if(node.son[pos] == null){<span style="white-space:pre">				</span>node.son[pos] = new TrieNode();<span style="white-space:pre">				</span>node.son[pos].val = letters[i];<span style="white-space:pre">			</span>}else{<span style="white-space:pre">				</span>node.son[pos].num++;<span style="white-space:pre">			</span>}<span style="white-space:pre">			</span>node = node.son[pos];<span style="white-space:pre">	</span>//使node指向儿子节点<span style="white-space:pre">		</span>}<span style="white-space:pre">		</span>node.isEnd = true;<span style="white-space:pre">	</span>}<span style="white-space:pre">	</span><span style="white-space:pre">	</span>// 计算单词前缀的数量<span style="white-space:pre">	</span>public int countPrefix(String prefix){<span style="white-space:pre">	</span><span style="white-space:pre">		</span>if(prefix == null || prefix.length() == 0)<span style="white-space:pre">			</span>return -1;<span style="white-space:pre">		</span><span style="white-space:pre">		</span>TrieNode node = root;<span style="white-space:pre">		</span>char[] letters = prefix.toCharArray();<span style="white-space:pre">		</span>for(int i = 0, len = prefix.length(); i< len; i++){<span style="white-space:pre">			</span>int pos = letters[i] - 'a';<span style="white-space:pre">			</span>if(node.son[pos] == null){<span style="white-space:pre">				</span>return 0;<span style="white-space:pre">			</span>}else{<span style="white-space:pre">				</span>node = node.son[pos];<span style="white-space:pre">			</span>}<span style="white-space:pre">		</span>}<span style="white-space:pre">		</span>return node.num;<span style="white-space:pre">	</span>}<span style="white-space:pre">	</span><span style="white-space:pre">	</span>// 在字典树中查找一个完全匹配的单词<span style="white-space:pre">	</span>public boolean has(String str){<span style="white-space:pre">	</span><span style="white-space:pre">		</span>if(str == null || str.length() == 0)<span style="white-space:pre">			</span>return false;<span style="white-space:pre">		</span><span style="white-space:pre">		</span>TrieNode node = root;<span style="white-space:pre">		</span>char[] letters = str.toCharArray();<span style="white-space:pre">		</span>for(int i = 0, len = str.length(); i< len; i++){<span style="white-space:pre">			</span>int pos = letters[i] - 'a';<span style="white-space:pre">			</span>if(node.son[pos] != null)<span style="white-space:pre">				</span>node = node.son[pos];<span style="white-space:pre">			</span>else<span style="white-space:pre">				</span>return false;<span style="white-space:pre">		</span>}<span style="white-space:pre">		</span>return node.isEnd;<span style="white-space:pre">	</span>}<span style="white-space:pre">	</span><span style="white-space:pre">	</span>// 前序遍历字典树<span style="white-space:pre">	</span>public void preTraverse(TrieNode node){<span style="white-space:pre">	</span><span style="white-space:pre">		</span>if(node != null){<span style="white-space:pre">			</span>System.out.print(node.val + "-");<span style="white-space:pre">			</span>for(TrieNode child : node.son){<span style="white-space:pre">				</span>preTraverse(child);<span style="white-space:pre">			</span>}<span style="white-space:pre">		</span>}<span style="white-space:pre">	</span>}<span style="white-space:pre">	</span><span style="white-space:pre">	</span>public TrieNode getRoot() {<span style="white-space:pre">		</span>return root;<span style="white-space:pre">	</span>}<span style="white-space:pre">	</span>public void setRoot(TrieNode root) {<span style="white-space:pre">		</span>this.root = root;<span style="white-space:pre">	</span>}<span style="white-space:pre">	</span>public static void main(String[] args) {<span style="white-space:pre">		</span>Trie tree = new Trie();<span style="white-space:pre">		</span>String[] strs={<span style="white-space:pre">			</span>"banana",<span style="white-space:pre">			</span>"band",<span style="white-space:pre">			</span>"bee",<span style="white-space:pre">			</span>"absolute",<span style="white-space:pre">			</span>"acm"<span style="white-space:pre">		</span>};<span style="white-space:pre">		</span>String[] prefix={<span style="white-space:pre">			</span>"ba",<span style="white-space:pre">			</span>"b",<span style="white-space:pre">			</span>"band",<span style="white-space:pre">			</span>"abc"<span style="white-space:pre">		</span>};<span style="white-space:pre">		</span><span style="white-space:pre">		</span>for(String str : strs){<span style="white-space:pre">			</span>tree.insert(str);<span style="white-space:pre">		</span>}<span style="white-space:pre">		</span><span style="white-space:pre">		</span>System.out.println(tree.has("abc"));<span style="white-space:pre">		</span>tree.preTraverse(tree.getRoot());<span style="white-space:pre">		</span>System.out.println();<span style="white-space:pre">		</span><span style="white-space:pre">		</span>//tree.printAllWords()<span style="white-space:pre">		</span>for(String pre : prefix){<span style="white-space:pre">			</span>int num = tree.countPrefix(pre);<span style="white-space:pre">			</span>System.out.println(pre + " " + num);<span style="white-space:pre">		</span>}<span style="white-space:pre">	</span>}}</p><p></p><p>接下来是把该程序该为C++代码：</p><p><pre name="code" class="cpp">

#include<iostream>

#include<string>

using namespace std;

const int size = 26;

class TrieNode{

public:

int num;
//有多少单词通过这个节点，即节点字符出现的次数，也说明了有多少son引用被用到，或者说有多少条被用到的树的边，或者说是该节点的度

TrieNode* son[size];
//所有儿子节点的指针

bool isEnd;
//是不是最后一个节点，即叶子节点

char val;
//节点的值

public:

TrieNode(){

num = 1;

isEnd = false;

// son = new TrieNode[26];
//有待商榷

for(int i = 0; i< size; i++)

son[i] = NULL;

}

};

class Trie{

private:

TrieNode* root;

public:

Trie(){

root = new TrieNode();

root->val = '*';//表示根节点的值

}

//在字典树中插入一个单词

void insert(string& str){

if(str == "" || str.length() == 0)

return;

TrieNode* node = root;

const char* letters = str.c_str();

for(size_t i = 0, len = str.length(); i< len; i++){

int pos = *(letters+i) - 'a';

if(node->son[pos] == NULL){

node->son[pos] = new TrieNode();

node->son[pos]->val = *(letters + i);

}else{

node->son[pos]->num ++;

}

node = node->son[pos];

}

node->isEnd = true;

}

// 计算单词前缀的数量

int countPrefix(string& prefix){

if(prefix == "" || prefix.length() == 0)

return -1;

TrieNode* node = root;

const char* letters = prefix.c_str();

for(size_t i = 0, len = prefix.length(); i< len; i++){

int pos = *(letters + i) - 'a';

if(node->son[pos] == NULL){

return 0;

}else{

node = node->son[pos];

}

}

return node->num;

}

// 在字典树中查找一个完全匹配的单词

bool has(string& str){

if(str == "" || str.length() == 0)

return false;

TrieNode* node = root;

const char* letters = str.c_str();

for(size_t i = 0, len = str.length(); i< len; i++){

int pos = *(letters + i) - 'a';

if(node->son[pos] != NULL)

node = node->son[pos];

else

return false;

}

return node->isEnd;

}

// 前序遍历字典树

void preTraverse(TrieNode* node){

if(node != NULL){

cout << node->val <<"-";

for(int i = 0; i< size; i++){

if(node->son[i] != NULL)

preTraverse(node->son[i]);

}

}

}

TrieNode* getRoot(){

return root;

}

};

int main(){

Trie* tree = new Trie();

string strs[5] = {

"banana",

"band",

"bee",

"absolute",

"acm"

};

string prefix[4]={

"ba",

"b",

"band",

"abc"

};

// for(int i = 0; i< (strs->length()); i++){

// for(int i = 0; i< sizeof(procedureList)/sizeof(string); i++){

for(int i = 0; i< 5; i++){

tree->insert(strs[i]);

}

string pre = "abc";

cout << (tree->has(pre)) << endl;

tree->preTraverse(tree->getRoot());

cout<<endl;

//tree.printAllWords()

// for(int i = 0; i< (prefix->length()); i++){

for(int i = 0; i< 4; i++){

int num = tree->countPrefix(prefix[i]);

cout<< prefix[i] << " " << num << endl;

}

return 0;

}