LeetCode-in-Java
2390. Removing Stars From a String
Medium
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 <= 105sconsists of lowercase English letters and stars*.- The operation above can be performed on
s.
Solution
public class Solution {
public String removeStars(String s) {
StringBuilder sb = new StringBuilder();
int stars = 0;
for (int i = s.length() - 1; i >= 0; --i) {
if (s.charAt(i) == '*') {
++stars;
} else if (stars > 0) {
--stars;
} else {
sb.append(s.charAt(i));
}
}
return sb.reverse().toString();
}
}