Removing Stars From a String

Problem Statement - link #

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.

Examples #

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 <= 10^5
• s consists of lowercase English letters and *.
• The operation above can be performed on any s.

Solutions #

class Solution {
public:
    string removeStars(string s) {
        vector<char> res;
        for (char c : s) {
            if (c != '*') {
                res.push_back(c);
            } else if (!res.empty()) {
                res.pop_back();
            }
        }
        string result(res.begin(), res.end());
        return result;
    }
};