C++ 实现trie树

实现一个trie数，包括insert(插入单词)、search(搜索单词)、startsWith(检查是否包含前缀)。输入的字符串只包含小写字符(a-z)。

#include<vector>
#include<string>
#define MAX_TRIE_CHAR_NUM 26
struct TrieNode
{
 TrieNode* child[MAX_TRIE_CHAR_NUM];
 bool is_end;
 TrieNode() : is_end(false)
 {
  for (int i = 0; i < MAX_TRIE_CHAR_NUM; i++)
  {
   child[i] = 0;
  }
 }
};
void get_all_word_from_trie(TrieNode* node, std::string& word, std::vector<std::string>& wordlist)
{
 for (int i = 0; i < MAX_TRIE_CHAR_NUM; i++)
 {
  if (node->child[i])
  {
   word.push_back(i + 'a');
   if (node->child[i]->is_end)
   {
    wordlist.push_back(word);
   }
   get_all_word_from_trie(node->child[i], word, wordlist);
   word.erase(word.length() - 1, 1);
  }
 }
}
void preorder_trie(TrieNode* node, int layer)
{
 for (int i = 0; i < MAX_TRIE_CHAR_NUM; i++)
 {
  if (node->child[i])
  {
   for (int j = 0; j < layer; j++)
   {
    printf("---");
   }
   printf("%c", i + 'a');
   if (node->child[i]->is_end)
   {
    printf("(end)");
   }
   printf("\n");
   preorder_trie(node->child[i], layer + 1);
  }
 }
}
class TrieTree
{
public:
 TrieTree() {}
 ~TrieTree()
 {
  for (int i = 0; i < _node_vec.size(); i++)
  {
   delete _node_vec[i];
  }
 }
 TrieNode _root;
 void insert(const char* word)
 {
  TrieNode* ptr = &_root;
  while (*word)
  {
   int pos = *word - 'a';
   if (!ptr->child[pos])
   {
    ptr->child[pos] = new_node();
   }
   ptr = ptr->child[pos];
   word++;
  }
  ptr->is_end = true;
 }
 bool search(const char* word)
 {
  TrieNode* ptr = &_root;
  while (*word)
  {
   int pos = *word - 'a';
   if (!ptr->child[pos])
   {
    return false;
   }
   ptr = ptr->child[pos];
   word++;
  }
  return ptr->is_end;
 }
 bool startsWith(const char* prefix)
 {
  TrieNode* ptr = &_root;
  while (*prefix)
  {
   int pos = *prefix - 'a';
   if (!ptr->child[pos])
   {
    return false;
   }
   ptr = ptr->child[pos];
   prefix++;
  }
  return true;
 }
private:
 TrieNode* new_node()
 {
  TrieNode* node = new TrieNode();
  _node_vec.push_back(node);
  return node;
 }
 std::vector<TrieNode*> _node_vec;
};
class Trie
{
public:
 Trie() {}
 ~Trie() {}
 void insert(std::string word)
 {
  _trie_tree.insert(word.c_str());
 }
 bool search(std::string word)
 {
  return _trie_tree.search(word.c_str());
 }
 bool startsWith(std::string prefix)
 {
  return _trie_tree.startsWith(prefix.c_str());
 }
private:
 TrieTree _trie_tree;
};
int main()
{
 Trie trie;
 trie.insert("abcde");
 printf("%d\n", trie.search("abcde"));
 printf("%d\n",trie.startsWith("abc"));
 printf("%d\n",trie.startsWith("abcdef"));
 printf("%d\n",trie.startsWith("abcde"));
 return 0;
}

运行结果为：

1
1
0
1