2390. Removing Stars From a String

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題目敘述

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.

解題思路

Solution

import java.util.Stack;

class Solution {
    public String removeStars(String s) {
        char[] toChar = s.toCharArray();
        Stack<Character> stack = new Stack<>();

        for(int i = 0; i < s.length(); i++){
            if(toChar[i] == '*'){
                stack.pop();
            }else {
                stack.add(toChar[i]);
            }
        }

        String ans = "";
        while(!stack.isEmpty()){
            ans = stack.pop() + ans;
        }

        return ans;
    }
}