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trieExample.cpp
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109 lines (82 loc) · 2.36 KB
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#include <iostream>
#include <bits/stdc++.h>
using namespace std;
/*
*
* Trie is an efficient information retrieval data structure.
* If keys are stored in binary search tree, a well balanced BST
* will need time proportional to M * log N, where M is maximum string
* length and N is number of keys in tree. Using Trie, we can search the key
* O(M) time. However the penalty is on Trie storage requirements.
*
* */
const int ALPHABET_SIZE = 26;
struct TrieNode
{
struct TrieNode *children[ALPHABET_SIZE];
bool isEndOfWord;
};
TrieNode *getNode(void)
{
struct TrieNode *pNode = new TrieNode;
pNode->isEndOfWord = false;
for(int i=0; i < ALPHABET_SIZE; i++)
{
pNode->children[i] = NULL;
}
return pNode;
}
void insert(struct TrieNode *root, string key)
{
struct TrieNode *pCrawl = root;
for(int i = 0; i < key.length(); i++)
{
int index = key[i] - 'a';
if(!pCrawl->children[index])
pCrawl->children[index] = getNode();
pCrawl = pCrawl->children[index];
}
pCrawl->isEndOfWord = true;
}
void display(struct TrieNode* root, char str[], int level)
{
if(root->isEndOfWord != false)
{
str[level] = '\0';
cout<<str<<endl;
}
for(int i=0; i < ALPHABET_SIZE; i++)
{
if(root->children[i])
{
str[level] = i + 'a';
display(root->children[i], str, level + 1);
}
}
}
bool search(struct TrieNode *root, string key)
{
struct TrieNode *pCrawl = root;
for(int i = 0; i < key.length(); i++)
{
int index = key[i] - 'a';
if(!pCrawl->children[index])
return false;
pCrawl = pCrawl->children[index];
}
return (pCrawl != NULL && pCrawl->isEndOfWord);
}
int main()
{
string keys[] = {"the", "a", "there", "answer", "any", "by", "bye", "their"};
int n = sizeof(keys)/sizeof(keys[0]);
struct TrieNode *root = getNode();
for(int i=0; i < n; i++)
insert(root, keys[i]);
search(root, "the") ? cout<<"Yes\n" : cout<<"No\n";
search(root, "there") ? cout<<"Yes\n" : cout<<"No\n";
search(root, "these") ? cout<<"Yes\n" : cout<<"No\n";
char str[20];
display(root, str, 0);
return 0;
}