2390. Removing Stars From a String
Description
You are given a string s
, which contains stars *
.
In one operation, you can:
- Choose a star in
s
. - Remove the closest non-star character to its left, as well as remove the star itself.
Return the string after all stars have been removed.
Note:
- The input will be generated such that the operation is always possible.
- It can be shown that the resulting string will always be unique.
Example 1:
Input: s = "leet**cod*e" Output: "lecoe" Explanation: Performing the removals from left to right: - The closest character to the 1st star is 't' in "leet**cod*e". s becomes "lee*cod*e". - The closest character to the 2nd star is 'e' in "lee*cod*e". s becomes "lecod*e". - The closest character to the 3rd star is 'd' in "lecod*e". s becomes "lecoe". There are no more stars, so we return "lecoe".
Example 2:
Input: s = "erase*****" Output: "" Explanation: The entire string is removed, so we return an empty string.
Constraints:
1 <= s.length <= 105
s
consists of lowercase English letters and stars*
.- The operation above can be performed on
s
.
Solutions
Solution 1: Stack Simulation
We can use a stack to simulate the operation process. Traverse the string $s$, and if the current character is not an asterisk, push it onto the stack; if the current character is an asterisk, pop the top element from the stack.
Finally, concatenate the elements in the stack into a string and return it.
The time complexity is $O(n)$, where $n$ is the length of the string $s$. Ignoring the space consumption of the answer string, the space complexity is $O(1)$.
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