'''
Given a non-negative integer num represented as a string, remove k digits from the number so that the new number is the smallest possible.

Note:
The length of num is less than 10002 and will be ≥ k.
The given num does not contain any leading zero.
Example 1:

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

# Solution::::::::::::::::::::::
class Solution:
    def removeKdigits(self, num: str, k: int) -> str:
        numStack=[]
        for digit in num:
            while k and numStack and numStack[-1] > digit:
                numStack.pop()
                k=k-1
            numStack.append(digit)
                
        finalStack = numStack[:k] if k else numStack
            
        return "".join(finalStack).lstrip('0') or "0"
        