trie completed

13_trie/01_construct_trie_from_scratch.cpp

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+/*
+    [intro]: https://youtu.be/6PX6wqDQE20?list=PLEJXowNB4kPyi859E6qGUs7jlpQehJndl
+    [insertion and search]: https://youtu.be/0k79LqIaHyQ?list=PLEJXowNB4kPyi859E6qGUs7jlpQehJndl
+    [deletion]: https://youtu.be/ict1UawpXMM?list=PLEJXowNB4kPyi859E6qGUs7jlpQehJndl
+
+    link (): https://www.geeksforgeeks.org/trie-insert-and-search/
+*/
+
+
+// ----------------------------------------------------------------------------------------------------------------------- //
+//CODE TO Count_Number_Of_Strings_With_Given_Prefix
+//Assumption: All characters are in lowercase
+#include<iostream>
+using namespace std;
+//#define NULL 0
+
+struct Trienode
+{
+    char data;
+    int wc;  //wc:word_count
+    Trienode* child[26];
+};
+Trienode nodepool[100000];  //Pool of 100K Trienodes
+Trienode* root;    //Root of Trie
+int poolcount;  //Always points to next free Trienode
+
+void init() //Initializer function
+{
+    poolcount = 0;
+    root = &nodepool[poolcount++];
+    root->data = '/';
+    for (register int i = 0;i < 26;++i)
+        root->child[i] = NULL;
+}
+
+Trienode* getNode(char c)
+{
+    Trienode* newnode = &nodepool[poolcount++];
+    newnode->data = c;
+    for (register int i = 0;i < 26;++i)
+        newnode->child[i] = NULL;
+    newnode->wc = 0;
+    return newnode;
+}
+
+void insert(char* s)
+{
+    Trienode* curr = root;
+    int index;
+    for (int i = 0; s[i] != '\0'; ++i)
+    {
+        index = s[i] - 'a';
+        if (curr->child[index] == NULL)
+            curr->child[index] = getNode(s[i]);
+        curr->child[index]->wc += 1;
+        curr = curr->child[index];
+    }
+}
+
+bool search(char* s)
+{
+    Trienode* curr = root;
+    int index;
+    for (int i = 0; s[i] != '\0'; ++i)
+    {
+        index = s[i] - 'a';
+        if (curr->child[index] == NULL || curr->child[index]->wc == 0)
+            return false;
+        curr = curr->child[index];
+    }
+    return true;
+}
+
+bool Triedelete(char* s)
+{
+    if (search(s))
+    {
+        Trienode* curr = root;
+        int index;
+        for (int i = 0; s[i] != '\0'; ++i)
+        {
+            index = s[i] - 'a';
+            curr->child[index]->wc -= 1;
+            curr = curr->child[index];
+        }
+    }
+}
+
+int countPrefix(string s)
+{
+    Trienode* curr = root;
+    int index;
+    for (int i = 0; s[i] != '\0'; ++i)
+    {
+        index = s[i] - 'a';
+        if (curr->child[index] == NULL || curr->child[index]->wc == 0)
+            return 0;   //No string with given prefix is present
+        curr = curr->child[index];
+    }
+    return curr->wc;
+}
+
+int main()
+{
+    init();
+    char a[5] = { 'a','r','m','y' };
+    char b[5] = { 'a','r','m' };
+    char c[5] = { 'a','r','m','s' };
+    char d[5] = { 'a','r','y' };
+    char e[5] = { 'a','m','y' };
+    char f[5] = { 'a','p','i' };
+
+
+    insert(a);
+    insert(b);
+    insert(c);
+    insert(d);
+    insert(e);
+    insert(f);
+
+    //cout<<search(b)<<"\n";
+
+    printf("No of strings with given prefix = %d\n", countPrefix("a"));
+    printf("No of strings with given prefix = %d\n", countPrefix("ar"));
+    printf("No of strings with given prefix = %d\n", countPrefix("arm"));
+    printf("No of strings with given prefix = %d\n", countPrefix("army"));
+    printf("No of strings with given prefix = %d\n", countPrefix("armi"));
+    printf("No of strings with given prefix = %d\n", countPrefix("ary"));
+
+    cout << "Deletion...STARTED\n";
+    Triedelete(a);
+    Triedelete(d);
+    cout << "DONE...\n\n";
+
+
+    printf("No of strings with given prefix = %d\n", countPrefix("a"));
+    printf("No of strings with given prefix = %d\n", countPrefix("ar"));
+    printf("No of strings with given prefix = %d\n", countPrefix("arm"));
+    printf("No of strings with given prefix = %d\n", countPrefix("army"));
+    printf("No of strings with given prefix = %d\n", countPrefix("armi"));
+    printf("No of strings with given prefix = %d\n", countPrefix("ary"));
+
+    return 0;
+}
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+/*
+    alternative way
+*/
+
+class Node {
+    public:
+    char data;
+    unordered_map<char, Node*> m;
+    bool isTerminal;
+
+    Node(char d) {
+        data = d;
+        isTerminal = false;
+    }
+};
+
+class Trie {
+    public:
+    Node* root;
+    Trie() {
+        root = new Node('\0');
+    }
+
+    void insert(string word) {
+        Node* temp = root;
+
+        for (char ch : word) {
+            if (temp->m.count(ch) == 0) {
+                temp->m[ch] = new Node(ch);
+            }
+            temp = temp->m[ch];
+        }
+        temp->isTerminal = true;
+    }
+
+    bool search(string word) {
+        Node* temp = root;
+
+        for (char ch : word) {
+            if (temp->m.count(ch) == 0) return false;
+            temp = temp->m[ch];
+        }
+        return temp->isTerminal;
+    }
+
+    // void delete(string word) {}
+};
+
+int main() {
+    string words[] = { "viren", "shiva", "tgvs", "new", "news" };
+
+    Trie t;
+    for (auto w : words) {
+        t.insert(w);
+    }
+
+    int q;
+    cin >> q;
+
+    string search_word;
+    while (q--) {
+        cin >> search_word;
+        if (t.search(search_word)) {
+            cout << "Yes, it is present" << endl;
+        }
+        else cout << "No, it is not present" << endl;
+    }
+
+    return 0;
+}

13_trie/02_Find_shortest_unique_prefix_for_every_word_in_a_given_list.cpp

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+/*
+    https://www.geeksforgeeks.org/find-all-shortest-unique-prefixes-to-represent-each-word-in-a-given-list/
+*/
+
+
+// ----------------------------------------------------------------------------------------------------------------------- //
+// C++ program to print all prefixes that
+// uniquely represent words.
+#include<bits/stdc++.h>
+using namespace std;
+
+#define MAX 256
+
+// Maximum length of an input word
+#define MAX_WORD_LEN 500
+
+// Trie Node.
+struct trieNode
+{
+    struct trieNode* child[MAX];
+    int freq; // To store frequency
+};
+
+// Function to create a new trie node.
+struct trieNode* newTrieNode(void)
+{
+    struct trieNode* newNode = new trieNode;
+    newNode->freq = 1;
+    for (int i = 0; i < MAX; i++)
+        newNode->child[i] = NULL;
+    return newNode;
+}
+
+// Method to insert a new string into Trie
+void insert(struct trieNode* root, string str)
+{
+    // Length of the URL
+    int len = str.length();
+    struct trieNode* pCrawl = root;
+
+    // Traversing over the length of given str.
+    for (int level = 0; level < len; level++)
+    {
+        // Get index of child node from current character
+        // in str.
+        int index = str[level];
+
+        // Create a new child if not exist already
+        if (!pCrawl->child[index])
+            pCrawl->child[index] = newTrieNode();
+        else
+            (pCrawl->child[index]->freq)++;
+
+            // Move to the child
+        pCrawl = pCrawl->child[index];
+    }
+}
+
+// This function prints unique prefix for every word stored
+// in Trie. Prefixes one by one are stored in prefix[].
+// 'ind' is current index of prefix[]
+void findPrefixesUtil(struct trieNode* root, char prefix[],
+    int ind)
+{
+    // Corner case
+    if (root == NULL)
+        return;
+
+        // Base case
+    if (root->freq == 1)
+    {
+        prefix[ind] = '\0';
+        cout << prefix << " ";
+        return;
+    }
+
+    for (int i = 0; i < MAX; i++)
+    {
+        if (root->child[i] != NULL)
+        {
+            prefix[ind] = i;
+            findPrefixesUtil(root->child[i], prefix, ind + 1);
+        }
+    }
+}
+
+// Function to print all prefixes that uniquely
+// represent all words in arr[0..n-1]
+void findPrefixes(string arr[], int n)
+{
+    // Construct a Trie of all words
+    struct trieNode* root = newTrieNode();
+    root->freq = 0;
+    for (int i = 0; i < n; i++)
+        insert(root, arr[i]);
+
+    // Create an array to store all prefixes
+    char prefix[MAX_WORD_LEN];
+
+    // Print all prefixes using Trie Traversal
+    findPrefixesUtil(root, prefix, 0);
+}
+
+// Driver function.
+int main()
+{
+    string arr[] = { "zebra", "dog", "duck", "dove" };
+    int n = sizeof(arr) / sizeof(arr[0]);
+    findPrefixes(arr, n);
+
+    return 0;
+}