public class Solution
extends Object
1505 - Minimum Possible Integer After at Most K Adjacent Swaps On Digits\.
Hard
You are 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.
**Constraints:**
* 1 <= num.length <= 3 * 104
* `num` consists of only **digits** and does not contain **leading zeros**.
* 1 <= k <= 104