字典树模板（java）

class Trie{
private int SIZE=26;
private TrieNode root;//字典树的根

Trie(){//初始化字典树
root=new TrieNode();
}

private class TrieNode{//字典树节点
private int num;//有多少单词通过这个节点,即节点字符出现的次数
private TrieNode[]  son;//所有的儿子节点
private boolean isEnd;//是不是最后一个节点
private char val;//节点的值

TrieNode(){
num=1;
son=new TrieNode[SIZE];
isEnd=false;
}
}

//建立字典树
public void insert(String str){//在字典树中插入一个单词
if(str==null||str.length()==0){
return ;
}
TrieNode node=root;
char[] letters=str.toCharArray();
for(int 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
public int countPrefix(String prefix){
if(prefix==null || prefix.length()==0){
return -1;
}
TrieNode node=root;
char[] letters=prefix.toCharArray();
for(int 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.
public boolean has(String str){
if(str==null || str.length()==0){
return false;
}
TrieNode node=root;
char[] letters = str.toCharArray();
for(int 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.
public void preTraverse(TrieNode node){
if(node!=null){
System.out.print(node.val+"-");
for(TrieNode child:node.son){
preTraverse(child);
}
}
}

public TrieNode getRoot(){
return this.root;
}

public static void main(String[] args){
Trie tree=new Trie();
String[] strs={"banana","band","bee","absolute","acm",};
String[]	prefix={"ba","b","band","abc",};
for(String str:strs){
tree.insert(str);
}
System.out.println(tree.has("abc"));
tree.preTraverse(tree.getRoot());
System.out.println();
for(String pre:prefix){
int num=tree.countPrefix(pre);
System.out.println(pre+" "+num);
}
}
}

<pre name="code" class="cpp">hdu 1251

#include<string>
#include<cstring>
#include<iostream>
#include<cstdio>

using namespace std;
#define SIZE 26

struct TNode{
int num;
char val;
TNode* son[SIZE];
bool isEnd;
TNode(){
num = 1;
isEnd = false;
for(int i = 0; i < SIZE; i ++)
son[i] = NULL;
}
};

class Trie{
private:
struct TNode* root;
public:
Trie(){
root = new TNode();
}
void insert(char* str){
if(strlen(str) == 0){
return ;
}
struct TNode* node = root;
for(int i = 0, len = strlen(str); i < len; i ++){
int pos = str[i] - 'a';
if(node->son[pos] == NULL){
node->son[pos] = new TNode();
node->son[pos]->val = str[i];
}else{
node->son[pos]->num ++;
}
node = node->son[pos];
}
node->isEnd = true;
}
int countPrefix(char* prefix){
if(strlen(prefix) == 0){
return 0;
}
struct TNode* node = root;
for(int i=0, len = strlen(prefix); i < len; i ++){
int pos = prefix[i] - 'a';
if(node->son[pos] != NULL){
node = node->son[pos];
}else{
return 0;
}
}
return node->num;
}
};
int main(){
Trie* node = new Trie();
char str[1010];
while(gets(str)){
if(strlen(str) == 0){
break;
}
node->insert(str);
}
while(scanf("%s", str) != EOF){
printf("%d\n", node->countPrefix(str));
}
return 0;
}

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