Remove K Digits
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.
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.
class Solution:
def removeKdigits(self, num, k):
"""
:type num: str
:type k: int
:rtype: str
"""
if not num or k == 0:
return num
if len(num) == k:
return "0"
stk = []
stk.append(num[0])
for n in num[1:]:
while stk and int(n) < int(stk[-1]) and k > 0:
stk.pop()
k -= 1
stk.append(n)
i = 0
while i < len(stk) and stk[i] == "0":
i += 1
if k == 0:
stk = stk[i:]
else:
stk = stk[i:-k]
if stk:
return ''.join(stk)
else:
return "0"