一、题目

2390. Removing Stars From a String

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**code". s becomes "leecod*e”.
• The closest character to the 2nd star is ‘e’ in “leecode”. 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.

二、题解

利用栈解决问题

class Solution {
public:string removeStars(string s) {int n = s.length();stack<char> st;string res = "";for(int i = 0;i < n;i++){char c = s[i];if(c != '*') st.push(c);else if(c == '*' && !st.empty()) st.pop();}while(st.size()) res += st.top(),st.pop();reverse(res.begin(),res.end());return res;}
};