LeetCode208—Implement Trie (Prefix Tree)

原题

看了WIKI才知道怎么回事。

原题链接

Implement a trie with insert, search, and startsWith methods.

Note:

You may assume that all inputs are consist of lowercase letters a-z.

分析

实现一个前缀树/字典树

要求实现插入、查找、前缀查找

class TrieNode {
public:
unordered_map<char ,TrieNode *>children;
bool isLeaf;
// Initialize your data structure here.
TrieNode():isLeaf(false)
{
}
};

class Trie {
public:
Trie() {
root = new TrieNode();
}

// Inserts a word into the trie.
void insert(string word) {
int length= word.size();
TrieNode*p=root;
for(int i=0;i<length;++i)
{
if(p->children.find(word[i])==p->children.end())
p->children[word[i]]=new TrieNode();
p=p->children[word[i]];
}
p->isLeaf=true;

}

// Returns if the word is in the trie.
bool search(string word) {
TrieNode*p=root;
int length=word.size();
for(int i=0;i<length;++i)
{
if(p->children.find(word[i])==p->children.end())
return false;
p=p->children[word[i]];
}
if(NULL!=p&&p->isLeaf)
return true;
else
return false;
}

// Returns if there is any word in the trie
// that starts with the given prefix.
bool startsWith(string prefix) {
TrieNode*p=root;
int length=prefix.size();
for(int i=0;i<length;++i)
{
if(p->children.find(prefix[i])==p->children.end())
return false;

p=p->children[prefix[i]];
}
return true;

}

private:
TrieNode* root;
};