Print all words matching a pattern in CamelCase Notation Dictionary

Given a dictionary of words where each word follows CamelCase notation, The task is to print all words in the dictionary that match with a given pattern consisting of uppercase characters only.

Note: CamelCase is the practice of writing compound words or phrases such that each word or abbreviation begins with a capital letter. Common examples include: “PowerPoint” and “WikiPedia”, “GeeksForGeeks”, “CodeBlocks”, etc.

Examples:

Input: dict[] = [“Hi”, “Hello”, “HelloWorld”,  “HiTech”, “HiGeek”, “HiTechWorld”, “HiTechCity”, “HiTechLab”], pattern  =”HT”,
Output: [“HiTech”, “HiTechWorld”, “HiTechCity”, “HiTechLab”]

Input: dict[] = [“Hi”, “Hello”, “HelloWorld”,  “HiTech”, “HiGeek”, “HiTechWorld”, “HiTechCity”, “HiTechLab”], pattern  =”H”,
Output: [“Hi”, “Hello”, “HelloWorld”,  “HiTech”, “HiGeek”, “HiTechWorld”, “HiTechCity”, “HiTechLab”]

Input: dict[] = [“Hi”, “Hello”, “HelloWorld”,  “HiTech”, “HiGeek”, “HiTechWorld”, “HiTechCity”, “HiTechLab”], pattern = “HTC”,
Output: [“HiTechCity”]

Input: dict[] = [“WelcomeGeek”,”WelcomeToGeeksForGeeks”, “GeeksForGeeks”], pattern = “WTG”,
Output: [“WelcomeToGeeksForGeeks”]

Input: dict[] = [“WelcomeGeek”,”WelcomeToGeeksForGeeks”, “GeeksForGeeks”], pattern = “GFG”,
Output: [GeeksForGeeks]

Input: dict[] = [“WelcomeGeek”,”WelcomeToGeeksForGeeks”, “GeeksForGeeks”], pattern = “GG”,
Output: No match found

Find Pattern in Camelcase Notation using Trie: 

Below is the idea to solve the problem:

Insert all dictionary keys into the Trie one by one. Here key refers to only Uppercase characters in original word in CamelCase notation.

• When encountering the key for the first time, mark the last node as leaf node and insert the complete word for that key into the vector associated with the leaf node. 
• If encountering a key that is already in the trie, update the vector associated with the leaf node with current word. 

After all dictionary words are processed, search for the pattern in the trie and print all words that match the pattern.

Follow the below steps to Implement the idea:

• Initialize a trie and insert Capital case letters in all the words in the trie.
• After inserting the word set bool isleaf to 1 and insert the word in the vector of string for the node of last character.
• Query for the pattern in trie and on the last character node of the pattern return the vector of strings. 

Below is the implementation of the above idea:

C++

// C++ program to print all words in the CamelCase
// dictionary that matches with a given pattern
#include <bits/stdc++.h>
using namespace std;

// Alphabet size (# of upper-Case characters)
#define ALPHABET_SIZE 26

// A Trie node
struct TrieNode
{
    TrieNode* children[ALPHABET_SIZE];

    // isLeaf is true if the node represents
    // end of a word
    bool isLeaf;

    // vector to store list of complete words
    // in leaf node
    list<string> word;
};

// Returns new Trie node (initialized to NULLs)
TrieNode* getNewTrieNode(void)
{
    TrieNode* pNode = new TrieNode;

    if (pNode)
    {
        pNode->isLeaf = false;

        for (int i = 0; i < ALPHABET_SIZE; i++)
            pNode->children[i] = NULL;
    }

    return pNode;
}

// Function to insert word into the Trie
void insert(TrieNode* root, string word)
{
    int index;
    TrieNode* pCrawl = root;

    for (int level = 0; level < word.length(); level++)
    {
        // consider only uppercase characters
        if (islower(word[level]))
            continue;

        // get current character position
        index = int(word[level]) - 'A';
        if (!pCrawl->children[index])
            pCrawl->children[index] = getNewTrieNode();

        pCrawl = pCrawl->children[index];
    }

    // mark last node as leaf
    pCrawl->isLeaf = true;

    // push word into vector associated with leaf node
    (pCrawl->word).push_back(word);
}

// Function to print all children of Trie node root
void printAllWords(TrieNode* root)
{
    // if current node is leaf
    if (root->isLeaf)
    {
        for(string str : root->word)
            cout << str << endl;
    }

    // recurse for all children of root node
    for (int i = 0; i < ALPHABET_SIZE; i++)
    {
        TrieNode* child = root->children[i];
        if (child)
            printAllWords(child);
    }
}

// search for pattern in Trie and print all words
// matching that pattern
bool search(TrieNode* root, string pattern)
{
    int index;
    TrieNode* pCrawl = root;

    for (int level = 0; level < pattern.length(); level++)
    {
        index = int(pattern[level]) - 'A';
        // Invalid pattern
        if (!pCrawl->children[index])
            return false;

        pCrawl = pCrawl->children[index];
    }

    // print all words matching that pattern
    printAllWords(pCrawl);

    return true;
}

// Main function to print all words in the CamelCase
// dictionary that matches with a given pattern
void findAllWords(vector<string> dict, string pattern)
{
    // construct Trie root node
    TrieNode* root = getNewTrieNode();

    // Construct Trie from given dict
    for (string word : dict)
        insert(root, word);

    // search for pattern in Trie
    if (!search(root, pattern))
        cout << "No match found";
}

// Driver function
int main()
{
    // dictionary of words where each word follows
    // CamelCase notation
    vector<string> dict = {
        "Hi", "Hello", "HelloWorld", "HiTech", "HiGeek",
        "HiTechWorld", "HiTechCity", "HiTechLab"
    };

    // pattern consisting of uppercase characters only
    string pattern = "HT";

    findAllWords(dict, pattern);

    return 0;
}

Java

// Java program to print all words in the CamelCase
// dictionary that matches with a given pattern
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
public class CamelCase {

    // Alphabet size (# of upper-Case characters)
    static final int ALPHABET_SIZE = 26;

    // A Trie node
    static class TrieNode {
        TrieNode[] children = new TrieNode[ALPHABET_SIZE];

        // isLeaf is true if the node represents
        // end of a word
        boolean isLeaf;

        // vector to store list of complete words
        // in leaf node
        List<String> word;

        public TrieNode() {
            isLeaf = false;
            for (int i = 0; i < ALPHABET_SIZE; i++)
                children[i] = null;

            word = new ArrayList<String>();
        }
    }

    static TrieNode root;

    // Function to insert word into the Trie
    static void insert(String word) {
        int index;
        TrieNode pCrawl = root;

        for (int level = 0; level < word.length(); level++) {

              // consider only uppercase characters
            if (Character.isLowerCase(word.charAt(level)))
                continue;

            // get current character position
            index = word.charAt(level) - 'A';
            if (pCrawl.children[index] == null)
                pCrawl.children[index] = new TrieNode();

            pCrawl = pCrawl.children[index];
        }

        // mark last node as leaf
        pCrawl.isLeaf = true;

        // push word into vector associated with leaf node
        (pCrawl.word).add(word);
    }

    // Function to print all children of Trie node root
    static void printAllWords(TrieNode root) {

        // if current node is leaf
        if (root.isLeaf) {
            for (String str : root.word)
                System.out.println(str);
        }

        // recurse for all children of root node
        for (int i = 0; i < ALPHABET_SIZE; i++) {
            TrieNode child = root.children[i];
            if (child != null)
                printAllWords(child);
        }
    }

    // search for pattern in Trie and print all words
    // matching that pattern
    static boolean search(String pattern) {
        int index;
        TrieNode pCrawl = root;

        for (int level = 0; level < pattern.length(); level++) {
            index = pattern.charAt(level) - 'A';

            // Invalid pattern
            if (pCrawl.children[index] == null)
                return false;

            pCrawl = pCrawl.children[index];
        }

        // print all words matching that pattern
        printAllWords(pCrawl);

        return true;
    }

    // Main function to print all words in the CamelCase
    // dictionary that matches with a given pattern
    static void findAllWords(List<String> dict, String pattern)
     {

        // construct Trie root node
        root = new TrieNode();

        // Construct Trie from given dict
        for (String word : dict)
            insert(word);

        // search for pattern in Trie
        if (!search(pattern))
            System.out.println("No match found");
    }

    // Driver function
    public static void main(String args[]) {

        // dictionary of words where each word follows
        // CamelCase notation
        List<String> dict = Arrays.asList("Hi", "Hello",
                           "HelloWorld", "HiTech", "HiGeek",
                          "HiTechWorld", "HiTechCity",
                            "HiTechLab");

        // pattern consisting of uppercase characters only
        String pattern = "HT";

        findAllWords(dict, pattern);
    }
}
// This code is contributed by Sumit Ghosh

C#

// C# program to print all words in
// the CamelCase dictionary that
// matches with a given pattern
using System;
using System.Collections.Generic;

class GFG
{

    // Alphabet size (# of upper-Case characters)
    static int ALPHABET_SIZE = 26;

    // A Trie node
    public class TrieNode
    {
        public TrieNode[] children = new
               TrieNode[ALPHABET_SIZE];

        // isLeaf is true if the node represents
        // end of a word
        public bool isLeaf;

        // vector to store list of complete words
        // in leaf node
        public List<String> word;

        public TrieNode()
        {
            isLeaf = false;
            for (int i = 0; i < ALPHABET_SIZE; i++)
                children[i] = null;

            word = new List<String>();
        }
    }

    static TrieNode root;

    // Function to insert word into the Trie
    static void insert(String word)
    {
        int index;
        TrieNode pCrawl = root;

        for (int level = 0;
                 level < word.Length; level++)
        {

            // consider only uppercase characters
            if (char.IsLower(word[level]))
                continue;

            // get current character position
            index = word[level] - 'A';
            if (pCrawl.children[index] == null)
                pCrawl.children[index] = new TrieNode();

            pCrawl = pCrawl.children[index];
        }

        // mark last node as leaf
        pCrawl.isLeaf = true;

        // push word into vector
        // associated with leaf node
        (pCrawl.word).Add(word);
    }

    // Function to print all children
    // of Trie node root
    static void printAllWords(TrieNode root)
    {

        // if current node is leaf
        if (root.isLeaf)
        {
            foreach (String str in root.word)
                Console.WriteLine(str);
        }

        // recurse for all children of root node
        for (int i = 0; i < ALPHABET_SIZE; i++)
        {
            TrieNode child = root.children[i];
            if (child != null)
                printAllWords(child);
        }
    }

    // search for pattern in Trie and
    // print all words matching that pattern
    static bool search(String pattern)
    {
        int index;
        TrieNode pCrawl = root;

        for (int level = 0;
                 level < pattern.Length;
                 level++)
        {
            index = pattern[level] - 'A';

            // Invalid pattern
            if (pCrawl.children[index] == null)
                return false;

            pCrawl = pCrawl.children[index];
        }

        // print all words matching that pattern
        printAllWords(pCrawl);

        return true;
    }

    // Main function to print all words
    // in the CamelCase dictionary that
    // matches with a given pattern
    static void findAllWords(List<String> dict,
                                  String pattern)
    {

        // construct Trie root node
        root = new TrieNode();

        // Construct Trie from given dict
        foreach (String word in dict)
            insert(word);

        // search for pattern in Trie
        if (!search(pattern))
            Console.WriteLine("No match found");
    }

    // Driver Code
    public static void Main(String []args)
    {

        // dictionary of words where each word follows
        // CamelCase notation
        List<String> dict = new List<String>{"Hi", "Hello",
                                             "HelloWorld", "HiTech",
                                             "HiGeek", "HiTechWorld",
                                             "HiTechCity", "HiTechLab"};

        // pattern consisting of
        // uppercase characters only
        String pattern = "HT";

        findAllWords(dict, pattern);
    }
}

// This code is contributed by Princi Singh

Python3

import string

# Alphabet size (# of upper-Case characters)
ALPHABET_SIZE = 26

class TrieNode:
    def __init__(self):
        self.children = [None]*ALPHABET_SIZE
        self.isLeaf = False
        self.word = []

# Returns new Trie node (initialized to NULLs)
def getNewTrieNode():
    pNode = TrieNode()
    return pNode

# Function to insert word into the Trie
def insert(root, word):
    pCrawl = root
    for level in range(len(word)):
        # consider only uppercase characters
        if word[level].islower():
            continue
        # get current character position
        index = ord(word[level]) - ord('A')
        if not pCrawl.children[index]:
            pCrawl.children[index] = getNewTrieNode()
        pCrawl = pCrawl.children[index]
    # mark last node as leaf
    pCrawl.isLeaf = True
    # push word into vector associated with leaf node
    (pCrawl.word).append(word)

# Function to print all children of Trie node root
def printAllWords(root):
    # if current node is leaf
    if root.isLeaf:
        for str in root.word:
            print(str)
    # recurse for all children of root node
    for i in range(ALPHABET_SIZE):
        child = root.children[i]
        if child:
            printAllWords(child)

# search for pattern in Trie and print all words
# matching that pattern
def search(root, pattern):
    pCrawl = root
    for level in range(len(pattern)):
        index = ord(pattern[level]) - ord('A')
        # Invalid pattern
        if not pCrawl.children[index]:
            return False
        pCrawl = pCrawl.children[index]
    # print all words matching that pattern
    printAllWords(pCrawl)
    return True

# Main function to print all words in the CamelCase
# dictionary that matches with a given pattern
def findAllWords(dict, pattern):
    # construct Trie root node
    root = getNewTrieNode()

    # Construct Trie from given dict
    for word in dict:
        insert(root, word)

    # search for pattern in Trie
    if not search(root, pattern):
        print("No match found")

# Driver function
if __name__ == '__main__':
    # dictionary of words where each word follows
    # CamelCase notation
    dict = [
        "Hi", "Hello", "HelloWorld", "HiTech", "HiGeek",
        "HiTechWorld", "HiTechCity", "HiTechLab"
    ]

    # pattern consisting of uppercase characters only
    pattern = "HT"

    findAllWords(dict, pattern)

Javascript

// Alphabet size (of upper-Case characters)
const ALPHABET_SIZE = 26;

// Class definition for TrieNode
class TrieNode {
    constructor() {
        // Children array to store all the children nodes
        this.children = Array(ALPHABET_SIZE).fill(null);
        // isLeaf property to check if the node is end of word
        this.isLeaf = false;
        // word property to store the word at this node
        this.word = [];
    }
}

// Function to get a new TrieNode
function getNewTrieNode() {
    const pNode = new TrieNode();
    return pNode;
}

// Function to insert a word into the Trie
function insert(root, word) {
    let pCrawl = root;
    // Traverse through each character of the word
    for (let level = 0; level < word.length; level++) {
        // Skip the character if it's not an uppercase letter
        if (!word[level].match(/[A-Z]/)) {
            continue;
        }
        // Get the index of the character
        const index = word.charCodeAt(level) - 'A'.charCodeAt(0);
        // If there is no node for this character, create a new one
        if (!pCrawl.children[index]) {
            pCrawl.children[index] = getNewTrieNode();
        }
        // Move the pointer to the child node
        pCrawl = pCrawl.children[index];
    }
    // Mark the node as end of word
    pCrawl.isLeaf = true;
    // Store the word at this node
    pCrawl.word.push(word);
}

// Function to print all the words stored at a TrieNode
function printAllWords(root) {
    // If the node is end of word, print all the words stored at this node
    if (root.isLeaf) {
        root.word.forEach((str) => {
            console.log(str);
        });
    }
    // Traverse through all the children nodes
    for (let i = 0; i < ALPHABET_SIZE; i++) {
        const child = root.children[i];
        // If there is a child node, call printAllWords for this node
        if (child) {
            printAllWords(child);
        }
    }
}

// Function to search for a pattern in Trie
function search(root, pattern) {
    let pCrawl = root;
    // Traverse through each character of the pattern
    for (let level = 0; level < pattern.length; level++) {
        // Get the index of the character
        const index = pattern.charCodeAt(level) - 'A'.charCodeAt(0);
        // If there is no node for this character, return false
        if (!pCrawl.children[index]) {
            return false;
        }
        // Move the pointer to the child node
        pCrawl = pCrawl.children[index];
    }
    // If the pattern is found, print all the words stored at the end node
    printAllWords(pCrawl);
    return true;
}

// function to find all the words matching the pattern
function findAllWords(dict, pattern) {
    // construct Trie root node
    const root = getNewTrieNode();

    // Construct Trie from given dict
    dict.forEach((word) => {
        insert(root, word);
    });

    // search for pattern in Trie
    if (!search(root, pattern)) {
        console.log("No match found");
    }
}

// main function to test the implementation

    // dictionary of words where each word follows
    // CamelCase notation
    const dict = ["Hi", "Hello", "HelloWorld", "HiTech", "HiGeek", "HiTechWorld", "HiTechCity", "HiTechLab"];
    // pattern consisting of uppercase characters only
    const pattern = "HT";

    findAllWords(dict, pattern);

Output

HiTech
HiTechCity
HiTechLab
HiTechWorld

Time complexity: O(n*m) where m is the length of the pattern and n is the length of the dictionary. 
Auxiliary Space: O(n)

Another Approach: Two Pointer 

Approach/Intuition:

Here, we are checking if the current word matches with the pattern or not. If it matches then we store that string. For checking we are using two pointer approach:

• If the character in ‘s’ matches the current character in ‘pattern’, then the function moves on to the next character in ‘pattern’. 
• If the character in ‘s’ is uppercase and does not match the current character in ‘pattern’, then the returns false. Returns true if it has reached the end of ‘s’ and matched every character in ‘pattern’, and false otherwise.

Follow the below steps to Implement the idea:

• Create an empty vector to store the words that match with the given pattern.
• For each word in Dictionary, it checks whether the word matches with pattern. If it does, insert that string in the answer and return the vector.
• In “check” function Initializes an integer “j” to 0, representing the current index of the pattern “pattern” that we are matching against
• If the character in “s” matches the current character in “pattern”, then increment “j” to move on to the next character in “pattern”.
• If the character in “s” is uppercase and does not match the current character in “pattern”, then return false because it means we have encountered an uppercase letter in “s” that does not match the corresponding character in “pattern”.
• Returns true if we have reached the end of “s” and matched every character in “pattern”, and false otherwise

Below is the code to implement the above approach:

C++

// C++ program to print all words in the CamelCase
// dictionary that matches with a given pattern
#include <bits/stdc++.h>
using namespace std;

bool check(string& s, string& pattern)
{
    // Initializes an integer "j" to 0, representing the
    // current index of the pattern "pattern" that we are
    // matching against
    int j = 0;
    int n = s.size();
    int m = pattern.size();
    for (int i = 0; i < n; i++) {
        // If the character in "s" matches the current
        // character in "pattern", then increment "j" to
        // move on to the next character in "pattern"
        if (s[i] == pattern[j]) {
            j++;
            // If the character in "s" is uppercase and does
            // not match the current character in "pattern",
            // then return false because it means we have
            // encountered an uppercase letter in "s" that
            // does not match the corresponding character in
            // "pattern"
        }
        else if (isupper(s[i]) && j != m) {
            return false;
        }
    }
    // Returns true if we have reached the end of "s" and
    // matched every character in "pattern", and false
    // otherwise
    return j == m;
}

vector<string> CamelCase(vector<string> dict,
                         string pattern)
{
    // Initializes an empty vector called "ans" to store the
    // words that match the pattern
    vector<string> ans;
    for (auto word : dict) {
        // Calls the "check" function to determine whether
        // the word matches the pattern "pattern"
        if (check(word, pattern)) {
            // If the word matches the pattern, add it to
            // the "ans" vector
            ans.push_back(word);
        }
    }
    // Returns the "ans" vector containing the words that
    // match the pattern
    return ans;
}

// Driver function
int main()
{
    // dictionary of words where each word follows
    // CamelCase notation
    vector<string> dict
        = { "Hi",         "Hello",    "HelloWorld",
            "HiTech",     "HiGeek",   "HiTechWorld",
            "HiTechCity", "HiTechLab" };

    // pattern consisting of uppercase characters only
    string pattern = "HT";

    // Call the CamelCase function and store the result in
    // "ans"
    vector<string> ans = CamelCase(dict, pattern);

    // Print the elements of the "ans" vector
    for (auto word : ans) {
        cout << word << endl;
    }

    return 0;
}
// this code is contributed by Ravi Singh

Python3

def check(s, pattern):
    # Initializes an integer "j" to 0, representing the
    # current index of the pattern "pattern" that we are
    # matching against
    j = 0
    n = len(s)
    m = len(pattern)
    for i in range(n):
        # If the character in "s" matches the current
        # character in "pattern", then increment "j" to
        # move on to the next character in "pattern"
        if j<m and s[i] == pattern[j]:
            j += 1
        # If the character in "s" is uppercase and does
        # not match the current character in "pattern",
        # then return false because it means we have
        # encountered an uppercase letter in "s" that
        # does not match the corresponding character in
        # "pattern"
        elif s[i].isupper() and j != m:
            return False
    # Returns true if we have reached the end of "s" and
    # matched every character in "pattern", and false
    # otherwise
    return j == m

def CamelCase(dict, pattern):
    # Initializes an empty list called "ans" to store the
    # words that match the pattern
    ans = []
    for word in dict:
        # Calls the "check" function to determine whether
        # the word matches the pattern "pattern"
        if check(word, pattern):
            # If the word matches the pattern, add it to
            # the "ans" list
            ans.append(word)
    # Returns the "ans" list containing the words that
    # match the pattern
    return ans

# Driver function
if __name__ == '__main__':
    # dictionary of words where each word follows
    # CamelCase notation
    dict = ["Hi", "Hello", "HelloWorld", "HiTech",
            "HiGeek", "HiTechWorld", "HiTechCity", "HiTechLab"]

    # pattern consisting of uppercase characters only
    pattern = "HT"

    # Call the CamelCase function and store the result in
    # "ans"
    ans = CamelCase(dict, pattern)

    # Print the elements of the "ans" list
    for word in ans:
        print(word)

Java

import java.util.*;

class Main {

    static boolean check(String s, String pattern) {
        // Initializes an integer "j" to 0, representing the
        // current index of the pattern "pattern" that we are
        // matching against
        int j = 0;
        int n = s.length();
        int m = pattern.length();
        for (int i = 0; i < n; i++) {
            // If the character in "s" matches the current
            // character in "pattern", then increment "j" to
            // move on to the next character in "pattern"
            if (j<m && s.charAt(i) == pattern.charAt(j)) {
                j++;
                // If the character in "s" is uppercase and does
                // not match the current character in "pattern",
                // then return false because it means we have
                // encountered an uppercase letter in "s" that
                // does not match the corresponding character in
                // "pattern"
            } else if (Character.isUpperCase(s.charAt(i)) && j != m) {
                return false;
            }
        }
        // Returns true if we have reached the end of "s" and
        // matched every character in "pattern", and false
        // otherwise
        return j == m;
    }

    static List<String> CamelCase(List<String> dict, String pattern) {
        // Initializes an empty list called "ans" to store the
        // words that match the pattern
        List<String> ans = new ArrayList<>();
        for (String word : dict) {
            // Calls the "check" function to determine whether
            // the word matches the pattern "pattern"
            if (check(word, pattern)) {
                // If the word matches the pattern, add it to
                // the "ans" list
                ans.add(word);
            }
        }
        // Returns the "ans" list containing the words that
        // match the pattern
        return ans;
    }

    // Driver function
    public static void main(String[] args) {
        // dictionary of words where each word follows
        // CamelCase notation
        List<String> dict = Arrays.asList("Hi", "Hello", "HelloWorld",
                "HiTech", "HiGeek", "HiTechWorld", "HiTechCity", "HiTechLab");

        // pattern consisting of uppercase characters only
        String pattern = "HT";

        // Call the CamelCase function and store the result in
        // "ans"
        List<String> ans = CamelCase(dict, pattern);

        // Print the elements of the "ans" list
        for (String word : ans) {
            System.out.println(word);
        }
    }
}

Output

HiTech
HiTechWorld
HiTechCity
HiTechLab

Time complexity:  O(n * m), where n is the number of words in the dictionary and m is the length of the pattern
Auxiliary Space: O(k), where k is the number of words in the dictionary that match the pattern

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