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 = 3
Output: "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 = 1
Output: "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 = 2
Output: "0"
Explanation: Remove all the digits from the number and it is left with nothing which is 0.
Constraints:
-
1 <= k <= num.length <= 105
-
num
consists of only digits. -
num
does not have any leading zeros except for the zero itself.
SOLUTION:
class Solution:
def removeKdigits(self, num: str, k: int) -> str:
n = len(num)
if n == k:
return "0"
stack = []
for i in range(n):
if len(stack) == 0:
stack.append(num[i])
else:
while len(stack) > 0 and int(num[i]) < int(stack[-1]) and len(stack) >= i - k + 1:
stack.pop()
if len(stack) == 0 or len(stack) < n - k:
stack.append(num[i])
return str(int("".join(stack)))
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