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208.cpp
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208.cpp
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#include <string>
#include <iostream>
#include <vector>
using namespace std;
class TrieNode {
public:
// Initialize your data structure here.
TrieNode():val(0),endHere(false) {
next = new TrieNode*[26]();
}
TrieNode(char c):val(c),endHere(false){
next = new TrieNode*[26]();
}
char val;
TrieNode** next;
bool endHere; // there exists a word ends here
};
class Trie {
public:
Trie() {
root = new TrieNode();
}
// Inserts a word into the trie.
void insert(string word) {
if(word.size()==0) return;
int firstDiffPos = 0;
TrieNode* lastCommon = findLastCommon(word, firstDiffPos);
string toInsert = word.substr(firstDiffPos);
insertString(lastCommon, toInsert);
}
// Returns if the word is in the trie.
bool search(string word) {
int firstDiffPos = 0;
TrieNode *lastCommon = findLastCommon(word, firstDiffPos);
return lastCommon->endHere && firstDiffPos==word.size();
}
// Returns if there is any word in the trie
// that starts with the given prefix.
bool startsWith(string prefix) {
int firstDiffPos = 0;
findLastCommon(prefix, firstDiffPos);
return firstDiffPos == prefix.size();
}
private:
TrieNode* root;
TrieNode* findLastCommon(string word, int &firstDiffPos){
if(word.size()==0) return root;
TrieNode* current = root;
TrieNode** currentNext = current->next;
while(firstDiffPos<word.size() && currentNext[word[firstDiffPos]-'a']!=NULL){
current = currentNext[word[firstDiffPos]-'a'];
firstDiffPos++;
currentNext = current->next;
}
return current;
}
void insertString(TrieNode* start, string word){
TrieNode *current = start;
for(int i=0;i<word.size();i++){
TrieNode* newNode = new TrieNode(word[i]);
TrieNode** currentNext = current->next;
currentNext[word[i]-'a'] = newNode;
current = newNode;
}
current->endHere = true;
}
};
// Your Trie object will be instantiated and called as such:
// Trie trie;
// trie.insert("somestring");
// trie.search("key");
int main(){
Trie t;
t.insert("a");
cout<<t.search("a")<<endl;
cout<<t.startsWith("a")<<endl;
return 0;
}