Sort an array of strings based on the given order | Set-2

• Last Updated : 08 Oct, 2021

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”, “geeksforgeeks”}, order[] = “hlabcdefgijkmnopqrstuvwxyz”
Output: hello geeksforgeeks
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 using namespace std; // Function to replace all the// characters in the array of strings// according to the given keyvoid hashFunction(vector& words,                  unordered_map key){    for (auto& x : words) {        for (int i = 0; i < x.size(); i++) {            x[i] = key[x[i]];        }    }} // Function to pring the strings// according to the given ordervoid printSorted(vector words, string order){    // Stores the characters in order    // to encode and decode the string    unordered_map 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 words = { "word", "world", "row" };    string order = "worldabcefghijkmnpqstuvxyz";     // Function Call    printSorted(words, order);     return 0;}

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 pring 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.

Javascript



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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