Given a number K and string str of digits denoting a positive integer, build the largest number possible by performing swap operations on the digits of str at most K times.

Example 1:

Input: K = 4, str = 1234567
Output:7654321
Explanation: Three swaps can make the
input 1234567 to 7654321, swapping 1
with 7, 2 with 6 and finally 3 with 5

Example 2:

Input: K = 3, str = 3435335
Output: 5543333
Explanation: Three swaps can make the 
input 3435335 to 5543333, swapping 3 
with 5, 4 with 5 and finally 3 with 4 

Your task:
Since this is a functional problem you don't have to worry about input, you just have to complete the function findMaximumNum(). There will be three arguments which will be provided. They are as such.
For Cpp: arguments - findMaximumNum(str, k, max) (str: string input, k: number, max: will contain result)
For Java: arguments - findMaximumNum(ar[], k, max) (ar[]: character array of input, k: number, max: will contain result).
You have to compute the result and store it in the "res" variable. The result will be printed by the driver code.

Expected Time Complexity: O( n! / (n-k)! ) , where n = length of input string
Expected Auxiliary Space: O(n)

Constraints:
1 ≤ |str| ≤ 30
1 ≤ K ≤ 10