# Sort an array of strings based on the given order

• Difficulty Level : Hard
• Last Updated : 29 Jun, 2021

Given an array of strings words[] and the sequential order of alphabets, our task is to sort the array according to the order given. Assume that the dictionary and the words only contain lowercase alphabets.

Examples:

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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: To solve the problem mentioned above we need to maintain the priority of each character in the given order. For doing that use Map Data Structure.

• Iterate in the given order and set the priority of a character to its index value.
• Use a custom comparator function to sort the array.
• In the comparator function, iterate through the minimum sized word between the two words and try to find the first different character, the word with the lesser priority value character will be the smaller word.
• If the words have the same prefix, then the word with a smaller size is the smaller word.

Below is the implementation of above approach:

## C++

 `// C++ program to sort an array``// of strings based on the given order` `#include ``using` `namespace` `std;` `// For storing priority of each character``unordered_map<``char``, ``int``> mp;` `// Custom comparator function for sort``bool` `comp(string& a, string& b)``{` `    ``// Loop through the minimum size``    ``// between two words``    ``for` `(``int` `i = 0;``         ``i < min(a.size(), b.size());``         ``i++) {` `        ``// Check if the characters``        ``// at position i are different,``        ``// then the word containing lower``        ``// valued character is smaller``        ``if` `(mp[a[i]] != mp[b[i]])``            ``return` `mp[a[i]] < mp[b[i]];``    ``}` `    ``/* When loop breaks without returning, it``       ``means the prefix of both words were same``       ``till the execution of the loop.``       ``Now, the word with the smaller size will``       ``occur before in sorted order``        ``*/``    ``return` `(a.size() < b.size());``}` `// Function to print the``// new sorted array of strings``void` `printSorted(vector words,``                 ``string order)``{` `    ``// Mapping each character``    ``// to its occurrence position``    ``for` `(``int` `i = 0; i < order.size(); i++)``        ``mp[order[i]] = i;` `    ``// Sorting with custom sort function``    ``sort(words.begin(), words.end(), comp);` `    ``// Printing the sorted order of words``    ``for` `(``auto` `x : words)``        ``cout << x << ``" "``;``}` `// Driver code``int` `main()``{` `    ``vector words``        ``= { ``"word"``, ``"world"``, ``"row"` `};``    ``string order``        ``= { ``"worldabcefghijkmnpqstuvxyz"` `};` `    ``printSorted(words, order);` `    ``return` `0;``}`

## Python3

 `# Python3 program to sort an array``# of strings based on the given order``from` `functools ``import` `cmp_to_key` `# For storing priority of each character``mp ``=` `{}` `# Custom comparator function for sort``def` `comp(a, b):``    ` `    ``# Loop through the minimum size``    ``# between two words``    ``for` `i ``in` `range``( ``min``(``len``(a), ``len``(b))):``        ` `        ``# Check if the characters``        ``# at position i are different,``        ``# then the word containing lower``        ``# valued character is smaller``        ``if` `(mp[a[i]] !``=` `mp[b[i]]):``            ``if` `mp[a[i]] < mp[b[i]]:``                ``return` `-``1``            ``else``:``                ``return` `1``    ` `    ``'''When loop breaks without returning, it``    ``means the prefix of both words were same``    ``till the execution of the loop.``    ``Now, the word with the smaller size will``    ``occur before in sorted order'''``    ``if` `(``len``(a) < ``len``(b)):``        ``return` `-``1``    ``else``:``        ``return` `1` `# Function to print the``# new sorted array of strings``def` `printSorted(words, order):``    ` `    ``# Mapping each character``    ``# to its occurrence position``    ``for` `i ``in` `range``(``len``(order)):``        ``mp[order[i]] ``=` `i``    ` `    ``# Sorting with custom sort function``    ``words ``=` `sorted``(words, key ``=` `cmp_to_key(comp))``    ` `    ``# Printing the sorted order of words``    ``for` `x ``in` `words:``        ``print``(x, end ``=` `" "``)` `# Driver code``words ``=` `[ ``"word"``, ``"world"``, ``"row"` `]``order ``=` `"worldabcefghijkmnpqstuvxyz"` `printSorted(words, order)` `# This code is contributed by Shivani`
Output:
`world word row`

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