# Sort an array of strings based on the given order

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:

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++ 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 occurance 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; ` `} `

Output:
```world word row
```

Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.

Check out this Author's contributed articles.

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.

Article Tags :
Practice Tags :