Given string num representing a non-negative integer `num`

, and an integer `k`

, return *the smallest possible integer after removing* `k`

*digits from* `num`

.

**Example 1:**

Input:num = "1432219", k = 3Output:"1219"Explanation:Remove the three digits 4, 3, and 2 to form the new number 1219 which is the smallest.

**Example 2:**

Input:num = "10200", k = 1Output:"200"Explanation:Remove the leading 1 and the number is 200. Note that the output must not contain leading zeroes.

**Example 3:**

Input:num = "10", k = 2Output:"0"Explanation:Remove all the digits from the number and it is left with nothing which is 0.

**Constraints:**

`1 <= k <= num.length <= 10`

^{5}`num`

consists of only digits.`num`

does not have any leading zeros except for the zero itself.

public class Solution {
public string RemoveKdigits(string num, int k) {
}
}