Given an array of strings words[] and the sequential order of alphabets, the task is to sort the array according to the given order. Assume that the dictionary and the words only contain lowercase English alphabets.
Examples:
Input: words[] = {“hello”, “neveropen”}, order[] = “hlabcdefgijkmnopqrstuvwxyz”
Output: hello neveropen
Explanation: According to the given order ‘h’ occurs before ‘g’ and hence the words are considered to be sorted.Input: words = {“word”, “world”, “row”}, order = “worldabcefghijkmnpqstuvxyz”
Output: world word row
Explanation: According to the given order ‘l’ occurs before ‘d’ hence the words “world” will be kept first.
Approach: The given problem is already discussed in the article here. This article suggests a different approach that uses hashing. Since an order of alphabets is given, it can be used as a key where order[i]th alphabet can be replaced by the ith alphabet. For instance, in the given order[] = “hlabcdefgijkmnopqrstuvwxyz”, character ‘h’ can be replaced by ‘a’, character ‘l’ can be replaced by ‘b’, and so on. Using that observation the given problem can be solved by following the below steps:
- Create a hashFunction that accepts a key as an argument and replaces all the characters of the string according to the given key i.e, character x will be replaced by character stored in key[x].
- Use an unordered map encode, which store the sequence of characters as per the given order i.e, encode[‘h’] = ‘a’, encode[‘l’] = ‘b’… and so on. Similarly, store the reverse in decode i.e, decode[‘a’] = ‘h’, decode[‘b’] = ‘l’… and so on which can be used to restore the original array.
- Sort the array after hashing it using encode as the key.
- Restore the strings in the sorted array using decode as the key.
Below is the implementation of the above approach:
C++
// C++ program of the above approach#include <bits/stdc++.h>using namespace std;// Function to replace all the// characters in the array of strings// according to the given keyvoid hashFunction(vector<string>& words, unordered_map<char, char> key){ for (auto& x : words) { for (int i = 0; i < x.size(); i++) { x[i] = key[x[i]]; } }}// Function to print the strings// according to the given ordervoid printSorted(vector<string> words, string order){ // Stores the characters in order // to encode and decode the string unordered_map<char, char> encode, decode; // Loop to iterate over all characters for (int i = 0; i < 26; i++) { // Replace the order[i]th character // from the ith character encode[order[i]] = 'a' + i; // Replace the ith character // from the order[i]th character decode['a' + i] = order[i]; } // Function Call to replace all characters // in words according to encode hashFunction(words, encode); // STL Function to sort the array sort(words.begin(), words.end()); // Function Call to replace all characters // in words according to decode in order // to restore original strings hashFunction(words, decode); // Printing the sorted order of words for (auto x : words) { cout << x << " "; }}// Driver codeint main(){ vector<string> words = { "word", "world", "row" }; string order = "worldabcefghijkmnpqstuvxyz"; // Function Call printSorted(words, order); return 0;} |
Java
// Java program of the above approachimport java.util.List;import java.util.ArrayList;import java.util.Collections;import java.util.Map;import java.util.HashMap;public class GFG { // Function to replace all the // characters in the array of strings // according to the given key static void hashFunction(List<String> words, Map<Character, Character> key) { for (int i = 0; i < words.size(); i++) { char[] ch = words.get(i).toCharArray(); for (int j = 0; j < words.get(i).length(); j++) { ch[j] = key.get(ch[j]); } words.set(i, new String(ch)); } } // Function to print the strings // according to the given order static void printSorted(List<String> words, String order) { // Stores the characters in order // to encode and decode the string Map<Character, Character> encode = new HashMap<>(); Map<Character, Character> decode = new HashMap<>(); // Loop to iterate over all characters for (int i = 0; i < 26; i++) { // Replace the order[i]th character // from the ith character encode.put(order.charAt(i), (char)('a' + i)); // Replace the ith character // from the order[i]th character decode.put((char)('a' + i), order.charAt(i)); } // Function Call to replace all characters // in words according to encode hashFunction(words, encode); // STL Function to sort the array Collections.sort(words); // Function Call to replace all characters // in words according to decode in order // to restore original strings hashFunction(words, decode); // Printing the sorted order of words for (String x : words) { System.out.print(x + " "); } } // Driver code public static void main(String[] args) { List<String> words = new ArrayList<>() {{ add("word"); add("world"); add("row"); }}; String order = "worldabcefghijkmnpqstuvxyz"; // Function Call printSorted(words, order); }}// This code is contributed by Harshad. |
Python3
# Python 3 program of the above approach# Function to replace all the# characters in the array of strings# according to the given keydef hashFunction(words, key): for x in words: x = list(x) for i in range(len(x)): x[i] = key[x[i]] x = ''.join(x)# Function to print the strings# according to the given orderdef printSorted(words, order): # Stores the characters in order # to encode and decode the string encode = {} decode = {} # Loop to iterate over all characters for i in range(26): # Replace the order[i]th character # from the ith character encode[order[i]] = chr(ord('a') + i) # Replace the ith character # from the order[i]th character decode[chr(ord('a') + i)] = order[i] # Function Call to replace all characters # in words according to encode hashFunction(words, encode) # STL Function to sort the array words.sort(reverse = True) # Function Call to replace all characters # in words according to decode in order # to restore original strings hashFunction(words, decode) # Printing the sorted order of words for x in words: print(x,end = " ")# Driver codeif __name__ == '__main__': words = ["word", "world", "row"] order = "worldabcefghijkmnpqstuvxyz" # Function Call printSorted(words, order) # This code is contributed by ipg2016107. |
C#
// C# program of the above approachusing System;using System.Collections.Generic;using System.Linq;class GFG{ // Function to replace all the // characters in the array of strings // according to the given key static void hashFunction(List<string> words, Dictionary<char, char> key) { for (int i = 0; i < words.Count; i++) { char[] ch = words[i].ToCharArray(); for (int j = 0; j < words[i].Length; j++) { ch[j] = key[ch[j]]; } words[i] = new string(ch); } } // Function to print the strings // according to the given order static void printSorted(List<string> words, string order) { // Stores the characters in order // to encode and decode the string Dictionary<char, char> encode = new Dictionary<char, char>(); Dictionary<char, char> decode = new Dictionary<char, char>(); // Loop to iterate over all characters for (int i = 0; i < 26; i++) { // Replace the order[i]th character // from the ith character encode[order[i]] = (char)('a' + i); // Replace the ith character // from the order[i]th character decode[(char)('a' + i)] = order[i]; } // Function Call to replace all characters // in words according to encode hashFunction(words, encode); // STL Function to sort the array words.Sort(); // Function Call to replace all characters // in words according to decode in order // to restore original strings hashFunction(words, decode); // Printing the sorted order of words foreach (string x in words) { Console.Write(x + " "); } } // Driver code static public void Main() { List<string> words = new List<string> { "word", "world", "row" }; string order = "worldabcefghijkmnpqstuvxyz"; // Function Call printSorted(words, order); }}// This code is contributed by ruchikabaslas. |
Javascript
<script>// Javascript program of the above approach// Function to replace all the// characters in the array of strings// according to the given keyfunction hashFunction(words, key) { for (x of words) { for (let i = 0; i < x.length; i++) { x[i] = key.get(x[i]); } } console.log(words);}// Function to print the strings// according to the given orderfunction printSorted(words, order) { // Stores the characters in order // to encode and decode the string let encode = new Map(); let decode = new Map(); // Loop to iterate over all characters for (let i = 0; i < 26; i++) { // Replace the order[i]th character // from the ith character encode.set(order[i], "a".charCodeAt(0) + i); // Replace the ith character // from the order[i]th character decode.set("a".charCodeAt(0) + i, order[i]); } // Function Call to replace all characters // in words according to encode hashFunction(words, encode); // Function to sort the array words.sort().reverse(); // Function Call to replace all characters // in words according to decode in order // to restore original strings hashFunction(words, decode); // Printing the sorted order of words for (x of words) { document.write(x + " "); }}// Driver codelet words = ["word", "world", "row"];let order = "worldabcefghijkmnpqstuvxyz";// Function CallprintSorted(words, order);</script> |
Output
world word row
Time Complexity: O(N*M*log(N)) where M is the average length of all the strings.
Auxiliary Space: O(1)
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