402. Remove K Digits
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:
We need to make the smallest number by removing K digits. So we will remove the digits that are largest from the left.
Ex- if the num is "654" and k is 1 then we will remove 6
Ex- if the num is "654" and k is 1 then we will remove 6
if the num is "456" and k is 1 then we will remove 6
We will keep a stack and whenever the current digit is smaller than the top of the stack we will pop the stack until k>0 and the stack is not empty and the current digit is smaller than the top.
Another condition is that the current digit is 0 and the size of the stack is 1 and only contains 0 so we need to pop it.
If we have iterated over num and still k>0 then we need to pop the stack until k>0.
Now we can get our answer easily.
Now we can get our answer easily.
See the code below for better understanding.
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