Given a string num representing the digits of a very large integer and an integer k. You are allowed to swap any two adjacent digits of the integer at most k times. Return the minimum integer you can obtain also as a string. Example 1: Input: num = "4321", k = 4 Output: "1342" Explanation: The steps to obtain the minimum integer from 4321 with 4 adjacent swaps are shown. Example 2: Input: num = "100", k = 1 Output: "010" Explanation: It's ok for the output to have leading zeros, but the input is guaranteed not to have any leading zeros. Example 3: Input: num = "36789", k = 1000 Output: "36789" Explanation: We can keep the number without any swaps. Example 4: Input: num = "22", k = 22 Output: "22" Example 5: Input: num = "9438957234785635408", k = 23 Output: "0345989723478563548" Constraints: 1 <= num.length <= 30000 num contains digits only and doesn't have leading zeros. 1 <= k <= 10^9