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Merge pull request ephremdeme#222 from mnb27/master
TRIE ds in c++
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‎Trie/Auto_Complete_using_TRIE.cpp‎

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// C++ program to demonstrate auto-complete feature
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// using Trie data structure.
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#include<bits/stdc++.h>
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using namespace std;
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// Alphabet size (# of symbols)
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#define ALPHABET_SIZE (26)
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// Converts key current character into index
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// use only 'a' through 'z' and lower case
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#define CHAR_TO_INDEX(c) ((int)c - (int)'a')
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// trie node
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struct TrieNode
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{
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struct TrieNode *children[ALPHABET_SIZE];
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// isWordEnd is true if the node represents
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// end of a word
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bool isWordEnd;
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};
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// Returns new trie node (initialized to NULLs)
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struct TrieNode *getNode(void)
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{
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struct TrieNode *pNode = new TrieNode;
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pNode->isWordEnd = false;
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for (int i = 0; i < ALPHABET_SIZE; i++)
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pNode->children[i] = NULL;
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return pNode;
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}
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// If not present, inserts key into trie. If the
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// key is prefix of trie node, just marks leaf node
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void insert(struct TrieNode *root, const string key)
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{
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struct TrieNode *pCrawl = root;
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for (int level = 0; level < key.length(); level++)
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{
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int index = CHAR_TO_INDEX(key[level]);
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if (!pCrawl->children[index])
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pCrawl->children[index] = getNode();
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pCrawl = pCrawl->children[index];
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}
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// mark last node as leaf
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pCrawl->isWordEnd = true;
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}
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// Returns true if key presents in trie, else false
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bool search(struct TrieNode *root, const string key)
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{
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int length = key.length();
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struct TrieNode *pCrawl = root;
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for (int level = 0; level < length; level++)
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{
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int index = CHAR_TO_INDEX(key[level]);
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if (!pCrawl->children[index])
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return false;
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pCrawl = pCrawl->children[index];
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}
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return (pCrawl != NULL && pCrawl->isWordEnd);
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}
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// Returns 0 if current node has a child
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// If all children are NULL, return 1.
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bool isLastNode(struct TrieNode* root)
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{
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for (int i = 0; i < ALPHABET_SIZE; i++)
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if (root->children[i])
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return 0;
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return 1;
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}
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// Recursive function to print auto-suggestions for given
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// node.
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void suggestionsRec(struct TrieNode* root, string currPrefix)
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{
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// found a string in Trie with the given prefix
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if (root->isWordEnd)
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{
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cout << currPrefix;
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cout << endl;
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}
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// All children struct node pointers are NULL
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if (isLastNode(root))
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return;
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for (int i = 0; i < ALPHABET_SIZE; i++)
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{
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if (root->children[i])
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{
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// append current character to currPrefix string
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currPrefix.push_back(97 + i);
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// recur over the rest
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suggestionsRec(root->children[i], currPrefix);
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}
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}
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}
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// print suggestions for given query prefix.
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int printAutoSuggestions(TrieNode* root, const string query)
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{
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struct TrieNode* pCrawl = root;
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// Check if prefix is present and find the
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// the node (of last level) with last character
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// of given string.
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int level;
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int n = query.length();
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for (level = 0; level < n; level++)
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{
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int index = CHAR_TO_INDEX(query[level]);
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// no string in the Trie has this prefix
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if (!pCrawl->children[index])
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return 0;
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pCrawl = pCrawl->children[index];
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}
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// If prefix is present as a word.
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bool isWord = (pCrawl->isWordEnd == true);
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// If prefix is last node of tree (has no
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// children)
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bool isLast = isLastNode(pCrawl);
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// If prefix is present as a word, but
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// there is no subtree below the last
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// matching node.
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if (isWord && isLast)
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{
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cout << query << endl;
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return -1;
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}
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// If there are are nodes below last
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// matching character.
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if (!isLast)
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{
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string prefix = query;
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suggestionsRec(pCrawl, prefix);
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return 1;
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}
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}
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// Driver Code
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int main()
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{
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struct TrieNode* root = getNode();
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insert(root, "hello");
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insert(root, "dog");
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insert(root, "hell");
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insert(root, "cat");
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insert(root, "a");
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insert(root, "hel");
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insert(root, "help");
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insert(root, "helps");
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insert(root, "helping");
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int comp = printAutoSuggestions(root, "hel");
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if (comp == -1)
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cout << "No other strings found with this prefix\n";
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else if (comp == 0)
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cout << "No string found with this prefix\n";
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return 0;
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}

‎Trie/Implement trie (Prefix tree).cpp‎

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#define MAX_NODES 10000
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class Trie {
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struct Trienode
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{
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char val;
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int count;
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int endsHere;
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Trienode *child[26];
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};
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Trienode *root;
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Trienode *getNode(int index)
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{
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Trienode *newnode = new Trienode;
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newnode->val = 'a'+index;
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newnode->count = newnode->endsHere = 0;
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for(int i=0;i<26;++i)
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newnode->child[i] = NULL;
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return newnode;
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}
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public:
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/** Initialize your data structure here. */
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Trie() {
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ios_base::sync_with_stdio(false);
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cin.tie(NULL);
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root = getNode('/'-'a');
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}
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/** Inserts a word into the trie. */
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void insert(string word) {
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Trienode *curr = root;
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int index;
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for(int i=0;i<word.length();++i)
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{
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index = word[i]-'a';
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if(curr->child[index]==NULL)
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curr->child[index] = getNode(index);
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curr->child[index]->count +=1;
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curr = curr->child[index];
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}
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curr->endsHere +=1;
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}
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/** Returns if the word is in the trie. */
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bool search(string word) {
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Trienode *curr = root;
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int index;
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for(int i=0;i<word.length();++i)
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{
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index = word[i]-'a';
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if(curr->child[index]==NULL)
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return false;
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curr = curr->child[index];
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}
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return (curr->endsHere > 0);
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}
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/** Returns if there is any word in the trie that starts with the given prefix. */
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bool startsWith(string prefix) {
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Trienode *curr = root;
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int index;
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for(int i=0;i<prefix.length();++i)
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{
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index = prefix[i]-'a';
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if(curr->child[index]==NULL)
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return false;
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curr = curr->child[index];
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}
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return (curr->count > 0);
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}
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};
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/**
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* Your Trie object will be instantiated and called as such:
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* Trie* obj = new Trie();
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* obj->insert(word);
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* bool param_2 = obj->search(word);
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* bool param_3 = obj->startsWith(prefix);
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*/

‎Trie/Trie.cpp‎

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//CODE TO Count_Number_Of_Strings_With_Given_Prefix
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//Assumption: All characters are in lowercase
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#include<iostream>
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using namespace std;
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//#define NULL 0
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struct Trienode
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{
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char data;
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int wc; //wc:word_count
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Trienode *child[26];
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};
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Trienode nodepool[100000]; //Pool of 100K Trienodes
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Trienode *root; //Root of Trie
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int poolcount; //Always points to next free Trienode
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void init() //Initializer function
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{
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poolcount = 0;
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root = &nodepool[poolcount++];
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root->data = '/';
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for(register int i=0;i<26;++i)
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root->child[i] = NULL;
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}
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Trienode *getNode(char c)
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{
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Trienode *newnode = &nodepool[poolcount++];
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newnode->data = c;
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for(register int i=0;i<26;++i)
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newnode->child[i] = NULL;
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newnode->wc=0;
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return newnode;
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}
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void insert(char *s)
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{
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Trienode *curr = root;
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int index;
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for(int i=0; s[i]!='\0'; ++i)
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{
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index = s[i]-'a';
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if(curr->child[index]==NULL)
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curr->child[index] = getNode(s[i]);
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curr->child[index]->wc += 1;
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curr = curr->child[index];
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}
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}
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bool search(char *s)
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{
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Trienode *curr = root;
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int index;
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for(int i=0; s[i]!='\0'; ++i)
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{
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index = s[i]-'a';
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if(curr->child[index]==NULL || curr->child[index]->wc == 0)
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return false;
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curr = curr->child[index];
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}
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return true;
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}
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bool Triedelete(char *s)
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{
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if(search(s))
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{
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Trienode *curr = root;
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int index;
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for(int i=0; s[i]!='\0'; ++i)
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{
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index = s[i]-'a';
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curr->child[index]->wc -=1;
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curr = curr->child[index];
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}
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}
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}
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int countPrefix(string s)
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{
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Trienode *curr = root;
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int index;
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for(int i=0; s[i]!='\0'; ++i)
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{
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index = s[i]-'a';
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if(curr->child[index]==NULL || curr->child[index]->wc == 0)
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return 0; //No string with given prefix is present
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curr = curr->child[index];
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}
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return curr->wc;
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}
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int main()
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{
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init();
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char a[5] = {'a','r','m','y'};
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char b[5] = {'a','r','m'};
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char c[5] = {'a','r','m','s'};
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char d[5] = {'a','r','y'};
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char e[5] = {'a','m','y'};
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char f[5] = {'a','p','i'};
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insert(a);
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insert(b);
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insert(c);
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insert(d);
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insert(e);
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insert(f);
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//cout<<search(b)<<"\n";
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printf("No of strings with given prefix = %d\n",countPrefix("a"));
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printf("No of strings with given prefix = %d\n",countPrefix("ar"));
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printf("No of strings with given prefix = %d\n",countPrefix("arm"));
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printf("No of strings with given prefix = %d\n",countPrefix("army"));
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printf("No of strings with given prefix = %d\n",countPrefix("armi"));
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printf("No of strings with given prefix = %d\n",countPrefix("ary"));
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cout<<"Deletion...STARTED\n";
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Triedelete(a);
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Triedelete(d);
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cout<<"DONE...\n\n";
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printf("No of strings with given prefix = %d\n",countPrefix("a"));
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printf("No of strings with given prefix = %d\n",countPrefix("ar"));
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printf("No of strings with given prefix = %d\n",countPrefix("arm"));
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printf("No of strings with given prefix = %d\n",countPrefix("army"));
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printf("No of strings with given prefix = %d\n",countPrefix("armi"));
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printf("No of strings with given prefix = %d\n",countPrefix("ary"));
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return 0;
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}

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