Given a sequence of words, print all anagrams together

Given an array of words, print all anagrams together. For example, if the given array is {“cat”, “dog”, “tac”, “god”, “act”}, then output may be “cat tac act dog god”.

Recommended: Please solve it on “PRACTICE ” first, before moving on to the solution.

We have discussed two different methods in the previous post. In this post, a more efficient solution is discussed.

Trie data structure can be used for a more efficient solution. Insert the sorted order of each word in the trie. Since all the anagrams will end at the same leaf node. We can start a linked list at the leaf nodes where each node represents the index of the original array of words. Finally, traverse the Trie. While traversing the Trie, traverse each linked list one line at a time. Following are the detailed steps.

1) Create an empty Trie
2) One by one take all words of input sequence. Do following for each word
…a) Copy the word to a buffer.
…b) Sort the buffer
…c) Insert the sorted buffer and index of this word to Trie. Each leaf node of Trie is head of a Index list. The Index list stores index of words in original sequence. If sorted buffe is already present, we insert index of this word to the index list.
3) Traverse Trie. While traversing, if you reach a leaf node, traverse the index list. And print all words using the index obtained from Index list.

C++

// An efficient program to print all anagrams together 
#include <stdio.h> 
#include <stdlib.h> 
#include <string.h> 
#include <ctype.h> 
  
#define NO_OF_CHARS 26 
  
// Structure to represent list node for indexes of words in 
// the given sequence. The list nodes are used to connect 
// anagrams at leaf nodes of Trie 
struct IndexNode 
{ 
    int index; 
    struct IndexNode* next; 
}; 
  
// Structure to represent a Trie Node 
struct TrieNode 
{ 
    bool isEnd;  // indicates end of word 
    struct TrieNode* child[NO_OF_CHARS]; // 26 slots each for 'a' to 'z' 
    struct IndexNode* head; // head of the index list 
}; 
  
  
// A utility function to create a new Trie node 
struct TrieNode* newTrieNode() 
{ 
    struct TrieNode* temp = new TrieNode; 
    temp->isEnd = 0; 
    temp->head = NULL; 
    for (int i = 0; i < NO_OF_CHARS; ++i) 
        temp->child[i] = NULL; 
    return temp; 
} 
  
/* Following function is needed for library function qsort(). Refer 
   http://www.cplusplus.com/reference/clibrary/cstdlib/qsort/ */
int compare(const void* a, const void* b) 
{  return *(char*)a - *(char*)b; } 
  
/* A utility function to create a new linked list node */
struct IndexNode* newIndexNode(int index) 
{ 
    struct IndexNode* temp = new IndexNode; 
    temp->index = index; 
    temp->next = NULL; 
    return temp; 
} 
  
// A utility function to insert a word to Trie 
void insert(struct TrieNode** root, char* word, int index) 
{ 
    // Base case 
    if (*root == NULL) 
        *root = newTrieNode(); 
  
    if (*word != '\0') 
        insert( &( (*root)->child[tolower(*word) - 'a'] ), word+1, index ); 
    else  // If end of the word reached 
    { 
        // Insert index of this word to end of index linked list 
        if ((*root)->isEnd) 
        { 
            IndexNode* pCrawl = (*root)->head; 
            while( pCrawl->next ) 
                pCrawl = pCrawl->next; 
            pCrawl->next = newIndexNode(index); 
        } 
        else  // If Index list is empty 
        { 
            (*root)->isEnd = 1; 
            (*root)->head = newIndexNode(index); 
        } 
    } 
} 
  
// This function traverses the built trie. When a leaf node is reached, 
// all words connected at that leaf node are anagrams. So it traverses 
// the list at leaf node and uses stored index to print original words 
void printAnagramsUtil(struct TrieNode* root, char *wordArr[]) 
{ 
    if (root == NULL) 
        return; 
  
    // If a lead node is reached, print all anagrams using the indexes 
    // stored in index linked list 
    if (root->isEnd) 
    { 
        // traverse the list 
        IndexNode* pCrawl = root->head; 
        while (pCrawl != NULL) 
        { 
            printf( "%s ", wordArr[ pCrawl->index ] ); 
            pCrawl = pCrawl->next; 
        } 
    } 
  
    for (int i = 0; i < NO_OF_CHARS; ++i) 
        printAnagramsUtil(root->child[i], wordArr); 
} 
  
// The main function that prints all anagrams together. wordArr[] is input 
// sequence of words. 
void printAnagramsTogether(char* wordArr[], int size) 
{ 
    // Create an empty Trie 
    struct TrieNode* root = NULL; 
  
    // Iterate through all input words 
    for (int i = 0; i < size; ++i) 
    { 
        // Create a buffer for this word and copy the word to buffer 
        int len = strlen(wordArr[i]); 
        char *buffer = new char[len+1]; 
        strcpy(buffer, wordArr[i]); 
  
        // Sort the buffer 
        qsort( (void*)buffer, strlen(buffer), sizeof(char), compare ); 
  
        // Insert the sorted buffer and its original index to Trie 
        insert(&root,  buffer, i); 
    } 
  
    // Traverse the built Trie and print all anagrms together 
    printAnagramsUtil(root, wordArr); 
} 
  
  
// Driver program to test above functions 
int main() 
{ 
    char* wordArr[] = {"cat", "dog", "tac", "god", "act", "gdo"}; 
    int size = sizeof(wordArr) / sizeof(wordArr[0]); 
    printAnagramsTogether(wordArr, size); 
    return 0; 
} 

Java

// An efficient program to print all  
// anagrams together     
import java.util.Arrays; 
import java.util.LinkedList; 
  
public class GFG  
{  
    static final int NO_OF_CHARS = 26; 
      
    // Class to represent a Trie Node 
    static class TrieNode 
    { 
        boolean isEnd;  // indicates end of word 
          
        // 26 slots each for 'a' to 'z' 
        TrieNode[] child = new TrieNode[NO_OF_CHARS]; 
          
        // head of the index list 
        LinkedList<Integer> head;  
          
        // constructor 
        public TrieNode()  
        { 
            isEnd = false; 
            head = new LinkedList<>(); 
            for (int i = 0; i < NO_OF_CHARS; ++i) 
                child[i] = null; 
        } 
    } 
       
    // A utility function to insert a word to Trie 
    static TrieNode insert(TrieNode root,String word, 
                                int index, int i) 
    { 
        // Base case 
        if (root == null) 
        { 
            root = new TrieNode(); 
        } 
          
        if (i < word.length() ) 
        { 
            int index1 = word.charAt(i) - 'a'; 
            root.child[index1] = insert(root.child[index1], 
                                       word, index, i+1 ); 
        } 
        else  // If end of the word reached 
        { 
            // Insert index of this word to end of 
            // index linked list 
            if (root.isEnd == true) 
            { 
                root.head.add(index); 
            } 
            else // If Index list is empty 
            { 
                root.isEnd = true; 
                root.head.add(index); 
            } 
        } 
        return root; 
    } 
  
    // This function traverses the built trie. When a leaf  
    // node is reached, all words connected at that leaf  
    // node are anagrams. So it traverses the list at leaf   
    // node and uses stored index to print original words 
    static void printAnagramsUtil(TrieNode root,  
                                      String wordArr[]) 
    { 
        if (root == null) 
            return; 
       
        // If a lead node is reached, print all anagrams 
        // using the indexes stored in index linked list 
        if (root.isEnd) 
        { 
            // traverse the list 
            for(Integer pCrawl: root.head) 
                System.out.println(wordArr[pCrawl]); 
        } 
       
        for (int i = 0; i < NO_OF_CHARS; ++i) 
            printAnagramsUtil(root.child[i], wordArr); 
    } 
       
    // The main function that prints all anagrams together.  
    // wordArr[] is input sequence of words. 
    static void printAnagramsTogether(String wordArr[],  
                                               int size) 
    { 
        // Create an empty Trie 
        TrieNode root = null; 
       
        // Iterate through all input words 
        for (int i = 0; i < size; ++i) 
        { 
            // Create a buffer for this word and copy the 
            // word to buffer 
            char[] buffer = wordArr[i].toCharArray(); 
             
            // Sort the buffer 
            Arrays.sort(buffer); 
       
            // Insert the sorted buffer and its original 
            // index to Trie 
            root = insert(root, new String(buffer), i, 0); 
              
        } 
          
        // Traverse the built Trie and print all anagrms 
        // together 
        printAnagramsUtil(root, wordArr); 
    } 
       
    // Driver program to test above functions 
    public static void main(String args[]) 
    { 
        String wordArr[] = {"cat", "dog", "tac", "god", 
                                        "act", "gdo"}; 
        int size = wordArr.length; 
        printAnagramsTogether(wordArr, size); 
    } 
} 
// This code is contributed by Sumit Ghosh 

C#

// An efficient C# program to print all  
// anagrams together  
using System; 
using System.Collections.Generic;  
  
class GFG  
{  
    static readonly int NO_OF_CHARS = 26;  
      
    // Class to represent a Trie Node  
    public class TrieNode  
    {  
        // indicates end of word  
        public bool isEnd;  
          
        // 26 slots each for 'a' to 'z'  
        public TrieNode[] child = new TrieNode[NO_OF_CHARS];  
          
        // head of the index list  
        public List<int> head;  
          
        // constructor  
        public TrieNode()  
        {  
            isEnd = false;  
            head = new List<int>();  
            for (int i = 0; i < NO_OF_CHARS; ++i)  
                child[i] = null;  
        }  
    }  
      
    // A utility function to insert a word to Trie  
    static TrieNode insert(TrieNode root,String word,  
                                int index, int i)  
    {  
        // Base case  
        if (root == null)  
        {  
            root = new TrieNode();  
        }  
          
        if (i < word.Length )  
        {  
            int index1 = word[i] - 'a';  
            root.child[index1] = insert(root.child[index1],  
                                    word, index, i + 1 );  
        }  
          
        // If end of the word reached  
        else 
        {  
            // Insert index of this word to end of  
            // index linked list  
            if (root.isEnd == true)  
            {  
                root.head.Add(index);  
            }  
              
            // If Index list is empty  
            else 
            {  
                root.isEnd = true;  
                root.head.Add(index);  
            }  
        }  
        return root;  
    }  
  
    // This function traverses the built trie.  
    // When a leaf node is reached, all words 
    // connected at that leaf node are anagrams.  
    // So it traverses the list at leaf node 
    // and uses stored index to print original words  
    static void printAnagramsUtil(TrieNode root,  
                                    String []wordArr)  
    {  
        if (root == null)  
            return;  
      
        // If a lead node is reached,  
        // print all anagrams using the 
        // indexes stored in index linked list  
        if (root.isEnd)  
        {  
            // traverse the list  
            foreach(int pCrawl in root.head)  
                Console.WriteLine(wordArr[pCrawl]);  
        }  
      
        for (int i = 0; i < NO_OF_CHARS; ++i)  
            printAnagramsUtil(root.child[i], wordArr);  
    }  
      
    // The main function that prints  
    // all anagrams together. wordArr[] 
    // is input sequence of words.  
    static void printAnagramsTogether(String []wordArr,  
                                            int size)  
    {  
        // Create an empty Trie  
        TrieNode root = null;  
      
        // Iterate through all input words  
        for (int i = 0; i < size; ++i)  
        {  
            // Create a buffer for this word   
            // and copy the word to buffer  
            char[] buffer = wordArr[i].ToCharArray();  
              
            // Sort the buffer  
            Array.Sort(buffer);  
      
            // Insert the sorted buffer and   
            // its original index to Trie  
            root = insert(root, new String(buffer), i, 0);  
              
        }  
          
        // Traverse the built Trie and   
        // print all anagrms together  
        printAnagramsUtil(root, wordArr);  
    }  
      
    // Driver code  
    public static void Main(String []args)  
    {  
        String []wordArr = {"cat", "dog", "tac", "god",  
                                        "act", "gdo"};  
        int size = wordArr.Length;  
        printAnagramsTogether(wordArr, size);  
    }  
}  
  
// This code is contributed by 29AjayKumar 

Output:

cat
tac
act
dog
god
gdo

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.

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My Personal Notes

Given a sequence of words, print all anagrams together | Set 2

Recommended: Please solve it on “PRACTICE ” first, before moving on to the solution.

C++

Java

C#

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