Sorting array of strings (or words) using Trie (original) (raw)

Last Updated : 2 Mar, 2023

Given an array of strings, print them in alphabetical (dictionary) order. If there are duplicates in input array, we need to print them only once.

Examples:

Input : "abc", "xy", "bcd" Output : abc bcd xy

Input : "geeks", "for", "geeks", "a", "portal", "to", "learn", "can", "be", "computer", "science", "zoom", "yup", "fire", "in", "data" Output : a be can computer data fire for geeks in learn portal science to yup zoom

Trie is an efficient data structure used for storing data like strings. To print the string in alphabetical order we have to first insert in the trie and then perform preorder traversal to print in alphabetical order.

Implementation:

CPP `

// C++ program to sort an array of strings // using Trie #include <bits/stdc++.h> using namespace std;

const int MAX_CHAR = 26;

struct Trie {

// index is set when node is a leaf
// node, otherwise -1;
int index;

Trie* child[MAX_CHAR];

/*to make new trie*/
Trie()
{
    for (int i = 0; i < MAX_CHAR; i++)
        child[i] = NULL;
    index = -1;
}

};

/* function to insert in trie / void insert(Trie root, string str, int index) { Trie* node = root;

for (int i = 0; i < str.size(); i++) {

    /* taking ascii value to find index of
      child node */
    char ind = str[i] - 'a';

    /* making new path if not already */
    if (!node->child[ind])
        node->child[ind] = new Trie();

    // go to next node
    node = node->child[ind];
}

// Mark leaf (end of word) and store
// index of word in arr[]
node->index = index;

}

/* function for preorder traversal / bool preorder(Trie node, string arr[]) { if (node == NULL) return false;

for (int i = 0; i < MAX_CHAR; i++) {
    if (node->child[i] != NULL) {

        /* if leaf node then print key*/
        if (node->child[i]->index != -1)
            cout << arr[node->child[i]->index] << endl;

        preorder(node->child[i], arr);
    }
}

}

void printSorted(string arr[], int n) { Trie* root = new Trie();

// insert all keys of dictionary into trie
for (int i = 0; i < n; i++)
    insert(root, arr[i], i);

// print keys in lexicographic order
preorder(root, arr);

}

// Driver code int main() { string arr[] = { "abc", "xy", "bcd" }; int n = sizeof(arr) / sizeof(arr[0]); printSorted(arr, n); return 0; }

Java

// Java program to sort an array of strings using Trie

// Author : Rohit Jain // GFG user_id : @rj03012002

import java.util.*;

public class GFG {

// Alphabet size
static final int MAX_CHAR = 26;

// trie node
static class Trie {

    // index is set when node is a leaf
    // node, otherwise -1;
    int index;

    Trie child[] = new Trie[MAX_CHAR];

    /*to make new trie*/
    Trie()
    {

        for (int i = 0; i < MAX_CHAR; i++)
            child[i] = null;
        index = -1;
    }
}

/* function to insert in trie */
static void insert(Trie root, String str, int index)
{

    Trie node = root;

    for (int i = 0; i < str.length(); i++) {
        /* taking ascii value to find index of
      child node */
        int ind = str.charAt(i) - 'a';

        /* making new path if not already */
        if (node.child[ind] == null)
            node.child[ind] = new Trie();

        // go to next node
        node = node.child[ind];
    }

    // Mark leaf (end of word) and store
    // index of word in arr[]
    node.index = index;
}

/* function for preorder traversal */
static boolean preorder(Trie node, String arr[])
{

    if (node == null) {

        return false;
    }

    for (int i = 0; i < MAX_CHAR; i++) {

        if (node.child[i] != null) {

            /* if leaf node then print key*/
            if (node.child[i].index != -1) {

                System.out.print(
                    arr[node.child[i].index] + " ");
            }

            preorder(node.child[i], arr);
        }
    }
    return false;
}

static void printSorted(String arr[], int n)
{

    Trie root = new Trie();

    // insert all keys of dictionary into trie
    for (int i = 0; i < n; ++i) {

        insert(root, arr[i], i);
    }

    // print keys in lexicographic order
    preorder(root, arr);
}

public static void main(String[] args)
{

    String arr[] = { "abc", "xy", "bcd" };

    int n = arr.length;

    printSorted(arr, n);
}

}

Python3

Python3 program to sort an array of strings

using Trie

MAX_CHAR = 26

class Trie:

# index is set when node is a leaf
# node, otherwise -1;
# to make new trie
def __init__(self):
    self.child = [None for i in range(MAX_CHAR)]
    self.index = -1

def to insert in trie

def insert(root,str,index):

node = root

for i in range(len(str)):

    # taking ascii value to find index of
    # child node 
    ind = ord(str[i]) - ord('a')

    # making new path if not already
    if (node.child[ind] == None):
        node.child[ind] = Trie()

    # go to next node
    node = node.child[ind]


# Mark leaf (end of word) and store
# index of word in arr[]
node.index = index

function for preorder traversal

def preorder(node, arr):

if (node == None):
    return False

for i in range(MAX_CHAR):
    if (node.child[i] != None):

        # if leaf node then print key
        if (node.child[i].index != -1):
            print(arr[node.child[i].index])

        preorder(node.child[i], arr)

def printSorted(arr,n):

root = Trie()

# insert all keys of dictionary into trie
for i in range(n):
    insert(root, arr[i], i)

# print keys in lexicographic order
preorder(root, arr)

Driver code

arr = [ "abc", "xy", "bcd" ] n = len(arr) printSorted(arr, n)

This code is contributed by shinjanpatra

C#

// C# program to sort an array of strings using Trie using System;

class GFG { static int MAX_CHAR = 26;

// trie node
public class Trie
{
    // index is set when node is a leaf node, otherwise -1
    public int index;

    public Trie[] child = new Trie[MAX_CHAR];

    // constructor to make a new trie node
    public Trie()
    {
        for (int i = 0; i < MAX_CHAR; i++)
            child[i] = null;
        index = -1;
    }
}

/* function to insert in trie */
 static void Insert(Trie root, string str, int index)
{
    Trie node = root;

    for (int i = 0; i < str.Length; i++)
    {
        /* taking ASCII value to find the index of the child node */
        int ind = str[i] - 'a';

        /* making a new path if not already */
        if (node.child[ind] == null)
            node.child[ind] = new Trie();

        // go to the next node
        node = node.child[ind];
    }

    // mark the leaf node (end of the word) and store the index of the word in arr[]
    node.index = index;
}

/* function for preorder traversal */
static void Preorder(Trie node, string[] arr)
{
    if (node == null)
    {
        return;
    }

    for (int i = 0; i < MAX_CHAR; i++)
    {
        if (node.child[i] != null)
        {
            /* if leaf node, then print the key */
            if (node.child[i].index != -1)
            {
                Console.WriteLine(arr[node.child[i].index] + " ");
            }

            Preorder(node.child[i], arr);
        }
    }
}

static void PrintSorted(string[] arr, int n)
{
    Trie root = new Trie();

    // insert all keys of the dictionary into the trie
    for (int i = 0; i < n; i++)
    {
        Insert(root, arr[i], i);
    }

    // print the keys in lexicographic order
    Preorder(root, arr);
}

static void Main(string[] args)
{
    string[] arr = { "abc", "xy", "bcd" };
    int n = arr.Length;

    PrintSorted(arr, n);
}

}

// This code is contributed by Aman Kumar.

JavaScript

`

Time Complexity: O(n*m) where n is the length of the array and m is the length of the longest word.
Auxiliary Space: O(n*m)