402. Remove K Digits - LeetCode Solution

class Solution:
    def removeKdigits(self, num: str, k: int) -> str:


        stack = []

        for i in range(len(num)):
            while stack and int(stack[-1]) > int(num[i]) and k:
                k-=1
                stack.pop()

            stack.append(num[i])


        while k:
            stack.pop()
            k-=1

        if  len(stack) == 0:
            return "0"
        else:

            a = int("".join(stack))


            return str(a)