# Sort the Array by reversing the numbers in it

Given an array arr[] of N non-negative integers, the task is to sort these integers according to their reverse

Examples:

Input: arr[] = {12, 10, 102, 31, 15}
Output: 10 31 12 15 102
Reversing the numbers:
12 -> 21
10 -> 01
102 -> 201
31 -> 13
15 -> 51
Sorting the reversed numbers: 01 13 21 51 201
Original sorted array: 10 13 12 15 102

Input: arr[] = {12, 10}
Output: 10 12

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach: The idea is to store each element with its reverse in a vector pair and then sort all the elements of the vector according to the reverse stored. Finally, print the elements in order.

Below is the implementation of the above approach:

## C++

 `// C++ implementation of the approach ` ` `  `#include ` `using` `namespace` `std; ` ` `  `// Function to return the ` `// reverse of n ` `int` `reversDigits(``int` `num) ` `{ ` `    ``int` `rev_num = 0; ` `    ``while` `(num > 0) { ` `        ``rev_num = rev_num * 10 + num % 10; ` `        ``num = num / 10; ` `    ``} ` `    ``return` `rev_num; ` `} ` ` `  `// Function to sort the array according to ` `// the reverse of elements ` `void` `sortArr(``int` `arr[], ``int` `n) ` `{ ` `    ``// Vector to store the reverse ` `    ``// with respective elements ` `    ``vector > vp; ` ` `  `    ``// Inserting reverse with elements ` `    ``// in the vector pair ` `    ``for` `(``int` `i = 0; i < n; i++) { ` `        ``vp.push_back( ` `            ``make_pair(reversDigits(arr[i]), ` `                      ``arr[i])); ` `    ``} ` ` `  `    ``// Sort the vector, this will sort the pair ` `    ``// according to the reverse of elements ` `    ``sort(vp.begin(), vp.end()); ` ` `  `    ``// Print the sorted vector content ` `    ``for` `(``int` `i = 0; i < vp.size(); i++) ` `        ``cout << vp[i].second << ``" "``; ` `} ` ` `  `// Driver code ` `int` `main() ` `{ ` `    ``int` `arr[] = { 12, 10, 102, 31, 15 }; ` `    ``int` `n = ``sizeof``(arr) / ``sizeof``(arr); ` ` `  `    ``sortArr(arr, n); ` ` `  `    ``return` `0; ` `} `

## Python3

 `# Python3 implementation of the approach ` ` `  `# Function to return the ` `# reverse of n ` `def` `reversDigits(num) : ` ` `  `    ``rev_num ``=` `0``; ` `    ``while` `(num > ``0``) : ` `        ``rev_num ``=` `rev_num ``*` `10` `+` `num ``%` `10``; ` `        ``num ``=` `num ``/``/` `10``; ` ` `  `    ``return` `rev_num; ` ` `  `# Function to sort the array according to ` `# the reverse of elements ` `def` `sortArr(arr, n) : ` ` `  `    ``# Vector to store the reverse ` `    ``# with respective elements ` `    ``vp ``=` `[]; ` ` `  `    ``# Inserting reverse with elements ` `    ``# in the vector pair ` `    ``for` `i ``in` `range``(n) : ` `        ``vp.append((reversDigits(arr[i]),arr[i])); ` ` `  `    ``# Sort the vector, this will sort the pair ` `    ``# according to the reverse of elements ` `    ``vp.sort() ` ` `  `    ``# Print the sorted vector content ` `    ``for` `i ``in` `range``(``len``(vp)) : ` `        ``print``(vp[i][``1``],end``=` `" "``); ` ` `  `# Driver code ` `if` `__name__ ``=``=` `"__main__"` `: ` ` `  `    ``arr ``=` `[ ``12``, ``10``, ``102``, ``31``, ``15` `]; ` `    ``n ``=` `len``(arr); ` ` `  `    ``sortArr(arr, n); ` ` `  `# This code is contributed by AnkitRai01 `

Output:

```10 31 12 15 102
```

Time Complexity: , where N is the size of the array

GeeksforGeeks has prepared a complete interview preparation course with premium videos, theory, practice problems, TA support and many more features. Please refer Placement 100 for details

My Personal Notes arrow_drop_up 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.

Improved By : AnkitRai01